















CERAMICS 

The art of the use of Clay 







A PRACTICAL 
CERAMIC DICTIONARY 

for 

The Potter, Tile and Terra Cotta 
Manufacturer, those engaged in 
the Silicate Industry, and Students 
of Ceramics 

By 

C MERTS ERANZHEIM 


Published By 

DEMAREST PUBLICATIONS, INC. 

45 East 17th Street, New York 

1924 




TPISS 

C O H 'l' 


Copyright, 1924, by 
C. M. Franzheim. 




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Printed by 

The Barnes Printing Co., Inc. 
229 West 28th St., New York 

.m 241°?4' 

©C1A7925?S^ 




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Dedicated 

to 

The Future Welfare 
of all 

Ceramic Students of 
The Ohio State University 
and others 

Wherever they may be. 




FOREWORD 

npiHERE are three classes of ceramic words, or 
words having ceramic significance. First, those 
which have a certain meaning and use to the potter, 
and also the same meaning and use to others. Sec¬ 
ond, certain specific words, or word meanings, which 
relate directly to the ceramic industry, and have no 
other meaning or use. Third, many other common 
words, with a general meaning, which may relate to 
other things, but which convey a certain definite sig¬ 
nificance to the potter, which they would not convey 
to others. These three classes of words form the 
ceramic language. 

This Dictionary of Ceramic Language, together 
with explanations of Ceramic Processes, common 
Ceramic Practices, and accepted Ceramic Formulas, 
although incomplete in this first issue, comprises 
most of those in common use, or connected or asso¬ 
ciated with those in use,—and its purpose is to serve 
as a medium of better communication between the 
various branches of this industry, and perpetuate it 
to posterity. 


C. MERTS FRANZHEIM. 







Ceramic Dictionary 


9 


A 

ABSORPTION—Almost all ceramic bodies have some 
power of absorption, even when fired to supposed vitrifica¬ 
tion. Red ink and fuchsine dye are the standard commer¬ 
cial tests for absorption. Many dense bodies which would 
not have the power to absorb water may still be sufficiently 
open to permit the penetration of one of these, and a body 
which would not absorb these can be considered com¬ 
pletely and perfectly non-absorbent, non-porous and amal¬ 
gamated, although very few such bodies exist where clay 
is used as a base. 

ADAMANT—An imaginary hard substance. A synonymous 
term for extreme hardness. 

ADAMANTINE SPAR—Corundum, a very hard natural 
Aluminum Oxide, used as an abrasive. 

AGATE-WARE—Ware either in body or glaze imitating 
the appearance of agate. 

AGGLOMERATIVE—Material used as a binding element 
in certain highly silicious refractory products in place of 
clays, feldspars, etc., so as to hold particles together with¬ 
out affecting their efficiency. These are Lime, Calcium, 
Magnesium Chloride, Alum, Potassium and Sodium Sili¬ 
cates, or certain iron oxides. 

AGGLUTINATIVE—Material used as a plastic element in 
non-plastic bodies to give sufficient bonding power for 
handling and forming, and yet burn out. These are glue, 
lichen, parchment gum, tar, dextrine and molasses. 

AGING—That process of permitting raw or made clays to 
age, or become old, under proper moisture conditions, so 
as to accelerate colloidal degeneration, and so improve the 
manufacturing qualities of a clay. 




10 


Ceramic Dictionary 


AIR—By weight air is 77% nitrogen and 23% oxygen. 

ALABASTER—Gypsum of a very fine texture. 

ALBANY DIP—A natural ferruginous clay uniformly melt¬ 
ing at cone 8, thus having pyrometric value. Also used 
as a glaze in certain products. 

ALBITE—Soda Feldspar, but not the variety in common 
reference to soda feldspar. 

ALKALI—Various compounds of Potassium, Sodium and 
Ammonia, or any substance having marked basic proper¬ 
ties. The stronger ones are caustic. 

ALKALINE—Having the properties of Alkalis. 

ALKALINE WATER—Almost all natural waters are neu¬ 
tral, but a water made alkaline is capable of retaining 
more clay in suspension, using less water, than a neutral 
water. See casting. 

ALLOPHANE—A translucent amorphous, hydrous sili¬ 
cate of alumina, of clay-like dimensions, but not a clay. 

ALLUVIAL—Clays, or any material formed by the de¬ 
posit of natural waters. 

ALLUVIUM—Soil or clay or earths which have been 
washed away from one place and deposited in another. 

ALUM—A sulphate of potassium and aluminum. 

ALUMINA—Oxide of Aluminum. The most widely dis¬ 
tributed of all earths. It is the base of all clays, and al¬ 
though all clays are aluminous, all aluminas are not clays. 

ALUMINOUS—Containing clay, or having a clay like 
nature. 




Ceramic Dictionary 


11 


ALUMINUM CHLORIDE—The re-agent used sometimes 
in casting slips to flocculate. Under certain conditions a 
clay slip, being used for casting, may contain too much 
sal soda or sodium carbonate, so that the clay particles 
pass beyond the satisfied deflocculent stage, which results 
in a precipitation or separation of the solution. Aluminum 
Chloride may, under certain conditions, neutralize this ac¬ 
tion and bring the solution back again to a better state for 
casting. A compound of aluminum and chlorine, very 
hygroscopic. Soluble in water acidulated with hydro¬ 
chloric acid but not completely soluble in water alone, 
owing to hydrolysis. 

ALUMINUM OXIDE—Alumina. Used in error some¬ 
times for glass making instead of the Aluminum Oxide, 
hydrated. 

ALUMINUM OXIDE, HYDRATED—Used in glass mak¬ 
ing sometimes in place of feldspar to strengthen the glass, 
and for the same reasons feldspar is used. But it does 
not have the efficiency of feldspar as it does not introduce 
potash along with the alumina, and costs more per batch 
weight. The un-hydrated form causes stones. 

AMATORII—A betrothal plaque. 

AMIANTHUS—A rock of an asbestos nature, of a com¬ 
position similar to clays, and having strong fibrous cohe¬ 
sive properties. 

AMORPHOUS—Having no definite form or structure. 
Not crystalline. 

AMORPHOUS FLINT—Flint made from a completely 
rotted quartz sand or rock and having no crystalline na¬ 
ture. 



12 


Ceramic Dictionary 


AMPERE—Unit of electrical current. 

AMPHIBOLE—Hornblende. 

ANALYSIS—The result of a chemical or mechanical inves¬ 
tigation of any material. Usually considered only chem¬ 
ically, but in Ceramics a mechanical knowledge of mate¬ 
rial is of great practical value, as the value of almost all 
ceramics is based on a pleasing appearance, structure and 
resistance: which are mechanical qualifications. 

ANNEALING—The process of cooling to reduce the brit¬ 
tleness of product. A very important factor in the glass 
industry, but having no value in any product with a clay 
base. 

ANORTHITE—Lime Feldspar. 

ANORTHOCLASE—Soda-potash Feldspar, in which the 
Soda content is larger than the Potash. The Spar which 
is commonly referred to as Soda Feldspar. 

ARCHITECTURAL TERRA COTTA—Terra Cotta us¬ 
ually, though not always, of an artistic nature and de¬ 
sign for use in building. 

ARGILLACEOUS—Pertaining to the nature of argil, or 
clay. Containing Clay. Clayey. 

ARTIFICIAL GAS—See Water Gas. 

ARTIFICIAL PORCELAIN—Soft porcelain. Porcelain 
made by using gypsum, alum, bones, etc., as an ingre¬ 
dient. Any porcelain made with a preponderance of ma¬ 
terial different from Natural or Hard Porcelain. See 
Natural Porcelain. 

AUGITITE—A volcanic rock of complex chemical com¬ 
position. 



Ceramic Dictionary 


13 


B 

BABBIT METAL—White Metal, an alloy containing 75- 
90% copper, with tin and antimony. 

BAGS—Usually a box-like structure of fire brick placed in 
kilns at the point of entrance of flame into the kiln for 
the purpose of controlling and directing the passage of 
flame, and to protect the products of the kiln. 

BALL CLAY—Also called Pipe Clay, Fat Clay, Bond Clay 
and Plastic Clay. Found almost everywhere, but for cera¬ 
mic purposes must usually be very free from metallic 
oxides. Is used as the principal plastic element in bodies 
and saggers to give sufficient strength for forming and 
handling, and in certain glazes for adhesive qualities. The 
prime requisite of Potters Ball Clay is plasticity and bond¬ 
ing power, although some varieties in being vitreous are 
an aid to vitrification. The best Potters Ball Clays come 
from the Tennessee-Kentucky District and England. The 
former residual clays, plastic and clean, but absorbent and 
porous as a rule. The latter very plastic and vitreous, but 
likely to contain large percentages of lignite and carbona¬ 
ceous matter. There are many varieties of both kinds. 
English Balls contain some alkalis, which account for their 
usual vitrification. All Ball Clays are best when weath¬ 
ered. 

BALL MILL—A cylindrical grinding mill of many designs 
and sizes, used for the pulverization of mixing of mate¬ 
rial, either wet or dry, usually having a hard porcelain 
lining, and using hard French pebbles as the grinding 
element. 

BARIUM CARBONATE—A neutralizing agent used in 
the brick, terra cotta and building tile industries to retard 
the whitening action heretofore common to finished struc- 



14 


Ceramic Dictionary 


tures. “Witherite” is the natural mineral 90-95% pure. 
Precipitated Barium Carbonate is the artificial product 
and is over 95% pure. 1% is proportion used in body. 

BARITE—Barium Sulphate. Heavy Spar. 

BASALT—Dark colored basic igneous rock of volcanic ori¬ 
gin, very tough and heavy. 

BASE—Certain compounds capable of reacting with acid 
to form salts such as the caustic alkalis, calcium oxide, 
ammonia, etc. 

BASIC—Having the qualities of a base, or containing basic 
compounds. 

BATS—Cast iron shelving for placing decorating ware in 
kiln for firing. 

BARYTES—Barium Sulphate. Not a ceramic material, 
but sometimes erroneously used instead of Barium Car¬ 
bonate. 

BAUXITE—A hydrate of alumina capable of withstanding 
intense heat. 

BERYL—An Aluminum Beryllium Silicate of extreme 
hardness and sometimes of great beauty. Aquamarine 
and emerald are varieties. 

BINDING AGENTS—In almost all branches of ceramics 
the binding agent for bodies is a very important and nec¬ 
essary physical element. Although most materials con¬ 
tain in themselves certain binding powers, they are us¬ 
ually insufficient to accomplish the desired results, and 
therefore require augmentation. This is done by the in¬ 
troduction of some material having strong cohesive na¬ 
ture. These are divided into two classes, the one for use 
in the body itself for the purpose of rendering the clay 




Ceramic Dictionary 


15 


mass workable, strong and cohesive, for the purpose of 
forming and handling in the unfired state; and those used 
for cementing and binding the constituent parts of a body 
together after a fire for the purpose of securing perma¬ 
nency and resistance of finished product. In the first 
class, Ball Clays, and some strong China Clays, Agglu- 
tinatives or other fat material are used for the working 
body, and Ball Clays in some glazes for adhesive quality. 
In the second class, vitreous Ball Clays, Agglomeratives, 
Feldspar, Water Glass and Lime are the principal bind¬ 
ing ingredients, all of which melt and bind by cooling 
again. The choice of the binding medium to be used in 
a body depends on the product to be made, the method 
and heat to be used, and the results desired. 

BIOTITE—Black or Green Mica of a complex formula, 
containing small quantities of iron, manganese, potas¬ 
sium, soda, alumina, etc., a very common ingredient of 
all feldspathic rock. The well known pepper like speck 
found in feldspar is very likely to be this mineral. 

BISCUIT WARE—Any clay ware having lost its chemical 
water through firing, but lacking a glaze. 

BISCUIT KILN—Kilns used for first burning of clay 
wares. 

BISMUTH OXIDE—An Oxide which could supplant 
white lead in a glaze, but is too fusible for ordinary 
practice. 

BISQUE WARE—Same as biscuit ware. Certain art wares 
of a very soft porcelain body sold in Bisque state. 

BITSTONE—Uniformly sized and graded grains of hard 
quartz rock used in ghlost saggers on which glazed ware 
rests to avoid sticking. Also used as a scouring agent. 



16 


Ceramic Dictionary 


BLACK SPECK—The black speck common to potting raw 
materials especially feldspar, or sometimes clays, is most 
likely to be Biotite Mica, though sometimes forms of iron. 

BLISTERS—A very common potting ailment in both body 
and glaze. May be caused by improper materials; im¬ 
proper grinding and mixing; improper lawning; ware 
going into kiln wet; a too rapid fire; or a too high fire; 
carbon dioxide gas from coarse whiting passing through 
the glaze making a bubble which does not seal again; or 
certain oxides absorbing more oxygen in early fire, and 
giving it up again in later fire, causing bubbles which do 
not seal up again. 

BLOATING—The swelling of a clay mass through the 
evolution of gases from it, very similar to the rising of 
bread from dough. The swelling results in the formation 
of gas bubbles or vesicles which by their pressure cause 
the increase in volume. Usually caused by the release of 
oxygen gases from lime or iron oxides. 

BLOCKS—The plaster of paris model made from original 
clay model to secure a permanency of the design and to 
be used for the making of cases and molds. 

BLUE—In all ages the most desired and popular of all 
ceramic colors. The blue glazed pottery of Egypt, 2000 
B.C., was popular for centuries with them. Chinese blue 
decorations are age old and known to all. Persian blue 
enamels outlived that civilization. Delft is blue. Copen¬ 
hagen blue, and blue decorations today exceed and outsell 
all others. 

BLUE SPAR—Lazulite. Phosphate of Alumina. 

BLUNGER—A large tank with revolving arms used for the 
disintegration and mixing of clays, or clay bodies, in 
water without grinding. 



Ceramic Dictionary 


17 


BODY GRINDING—That process in the preparation of a 
clay body in which the clay slip is passed through or into 
some form of grinding mill, not so much for the purpose 
of regrinding the already pulverized and prepared mate¬ 
rial, as to secure a better incorporation, better dissem¬ 
ination and closer mixing of constituent ingredients so as 
to secure finished ware of finer texture, although a little 
grinding of some of the coarser material is secured. In 
some plants, the preliminary mixing is made directly in 
this mill, omitting the blunger operation. 

BONE ASH—Phosphate of Lime. An ingredient of bone 
china. 

BONE CHINA—China made from calcined bones, phos¬ 
phate of lime. Also known as phosphated porcelain. It 
has an advantage of firing and decorating at lower tem¬ 
peratures, but lacks hardness and wearing qualities, al¬ 
though very beautiful ware may be produced. 

BOND CLAY—A Ball Clay. A fat Clay. A plastic Clay. 
See Ball Clay. 

BORACIC ACID—Boric Acid, a hydrous oxide of Boron 
refined from Borate of Lime, a natural product found in 
California, Nevada and Tibet, or found in Tuscany in 
natural state. Under kiln action is reduced to 56% Boric 
Acid, 44% of water. Is used in all finer quality glass and 
most glazes, and enamels as a flux. 

BORAX—Sodium tetraborate, a refined crystalline salt. 
Is found as borate of lime in California, Nevada and Tibet. 
Under kiln action is reduced to 36% boric oxide plus 16% 
sodium oxide and 47% water. Used in enamels, glass 
and glaze as a fluxing element. 

BORIC ACID—Same as Boracic Acid. 



18 


Ceramic Dictionary 


BORON—The base element of all Borax compounds and 
Boric Acid. 

BOTTCHER—John F. A foremost German Potter about 
1701. The discoverer and developer of first true porce¬ 
lain, at Dresden factory. 

BRICK—Blocks of almost every kind of clay, or clays, 
fired or unfired, used for building or resistance. 

BRISTOL GLAZE—A raw opaque glaze used in covering 
stoneware products. 

BROOKITE—Titanium dioxide. May be brown, black- 
brown or black, opaque or transparent crystals. 

BRONGNIART—Alexander. Foremost French Potter, 

1812. The developer of Sevres ware greatest products. 

B.T.U.—British Thermal Unit. A measure of heat. The 
heat required to raise the temperature of one pound of 
water one degree. 

BROWN SPECKS—The brown, or reddish brown speck 
common to pottery materials is most likely to be some 
form of iron. 

BUBBLES—See Blisters. 

BUNG—A tier of saggers, or ware, super-imposed. 

BURR MILL—A circular flat grinding pan using hard 
granite like flat heavy stones set in the base, and by 
means of heavy revolving arms moving the same kind of 
stone over the base for the purpose of grinding in water 
only. 

BUTTERFLY—Same as creeping, crawling, and jumping, 
in which the glaze may run or draw up to certain por¬ 
tions of ware, leaving certain other portions dry, insuffi¬ 
ciently glazed, and rough. 




Ceramic Dictionary 


19 


c 

CALCAREOUS—Containing lime, or its compounds. Lime 
like. 

CALCINE—The action of heat on material, usually a pre¬ 
liminary process in the preparation of some material. A 
lime kiln is a calcining process, in which the Carbonic Acid 
is liberated from limestone in order to reduce to a pow¬ 
der or more workable condition, and disintegrate. Bones 
are calcined in order to reduce to a powder and remove 
organic matter. Quartz Rock is calcined in order to 
break down the hard structure and disintegrate, so as to 
make workable for grinding. Many ceramic materials, 
especially clays, are calcined to liberate all mechanical 
and chemical water so as to reduce shrinkage, or for the 
purpose of purification by a subsequent selection. Frit 
is a calcining process which renders soluble material in¬ 
soluble. In the production of many fine continental por¬ 
celains most of the material for glaze, as well as some 
for body, is calcined. Calcination is a very important pro¬ 
cess for the production of certain high class porcelain 
products, especially glazes. 

CALORIE—A unit of heat. The heat required to raise 
temperature of one kilo of water one degree. 

CAMEO—Cut out in raised relief. Opposite to Intaglio. 

CAP—Same as Hilliers. 

CAPILLARY—The action of the attraction or repulsion of 
a liquid by a solid. 

CARBONACEOUS—Containing carbon, or its compounds. 
Coal like. 

CARE—The human elemental constituent of all successful 
ceramic products. 



20 


Ceramic Dictionary 


CASE—The plaster of paris form from which plaster of paris 
working molds are made. The Case is made from the 
block and the block from the original model. 

CASTING—That process in the manufacture of clay prod¬ 
ucts by the use of clay slips poured into molds which ab¬ 
sorb the moisture from the clay and deposit the clay to 
form the desired shape, which when sufficiently dry is re¬ 
moved from the mold and finished. By this process it is 
desired to use the minimum amount of water in the slip in 
order to secure the greatest amount of clay so that the 
least amount of water will be handled and be required to 
be absorbed by the mold, thus getting the maximum work 
out of the mold. As alkaline water is capable of dissolving 
and retaining in suspension more clay material than a neu¬ 
tral or an acid water, it is therefore desired to make the 
casting water alkaline. This is done by the use of Sodium 
Silicate, Sal Soda or other compounds. This alkalinity 
not only dissolves the maximum amount of clay material, 
but if strongly alkaline will actually result in a defloccula¬ 
tion of the clay particles, and if carried to excess may ac¬ 
tually cause a precipitation of some of the clay particles, 
which would prove very undesirable as such precipitation 
would result in separation of the clay as a homogeneous 
mass. In casting, certain benefits are derived in certain 
products which cannot be secured by pressing or jigger- 
ing. Thicknesses may be better controlled, and, depend¬ 
ent upon the article produced, has certain advantages over 
the clay method of production. A highly silicious or non¬ 
plastic body may be made by casting which could not be 
made satisfactorily or economically in any other manner. 
Cast articles do not have the stress common to pressed 
articles, and the constituent parts of a cast body are more 
closely amalgamated than by a pressed one, and resultant 
clay particles do not form themselves into lines or circles 



Ceramic Dictionary 


21 


common to pressed or machine made articles. From the 
economic standpoint certain wares may be made more 
efficiently and more economically with less potting knowl¬ 
edge than any other process, dependent upon how any par¬ 
ticular casting process may be installed and established. 

CAUSTIC SODA —Sodium Hydrate. An alkali. A glass 
constituent used as a strong fluxing agent. 

CENTIMETER —A unit of length. 

CERAMICS —Also spelled Keramics. From the Greek God, 
Ceramos, patron saint of the Potter, 600 B.C. Ceramics 
is the art of the use of clay, or the art of the decoration of 
clay articles. Name sometimes used for the small vit¬ 
reous floor tile. 

CHASER MILL —A heavy structure crushing machine in 
which very heavy dense circular stones revolve on edge 
over a heavy stone base. Used for preliminary crushing 
of heavy rock. 

CHEMICAL PORCELAIN— High Fire Porcelain of the 
purest ceramic materials capable of resisting rapid heating 
and cooling, without cracking, and having a very hard 
glaze capable of resisting the action of chemicals. 

CHEMICAL WATER —That water held in chemical com¬ 
bination with other ingredients of a body as a compound, 
not free, and which cannot be liberated in ordinary cera¬ 
mic material before 350° Cent, is reached, but all of 
which is liberated between 350° Cent, and 700° Cent. 

CIMOLITE —A hydrous silicate of alumina; a clay like 
substance and composition similar to clay, but not a clay. 

CHROMIUM —Usually Chromium Oxide. A green color¬ 
ing agent used in glazes, but care is required both with 
nature of glaze ingredients used with it, and the atmo¬ 
spheric kiln conditions of firing to secure desired results. 



22 


Ceramic Dictionary 


CHINA —As applied to ceramic products, a very much 
abused word. Is used for almost any kind of clay prod¬ 
ucts. Usually indicating vitrification but not always 
translucency. 

CHINA CLAY —Hydrate Silica of Alumina. Made in na¬ 
ture by the rotting of feldspar, or feldspathic rock, such 
as granite. The purer the rock, the purer clay is likely 
to be, but as almost all feldspathic rock contains micas, 
quartz, garnet and iron compounds, these are all likely 
to be found in clays, especially those of primary origin 
and require the most careful washing processes to purify. 
In the production of the first grade of English China 
Clays as much as 80% impurity may be removed. Sec¬ 
ondary China Clays are usually washed by natural waters 
in the process of water transportation. In pome cases this 
cleansing process is most perfect in removing original im¬ 
purities, but high quality secondary clays are rare as 
this transportation usually introduces and diffuses some 
foreign substance into the deposit, impossible to remove, 
or may cause other undesirable, unalterable changes. The 
formula for pure Clay would be 39.77% Alumina, 46.33% 
Silica and 13.90% water. 

CHINA STONE —Same as Cornwall Stone. 

COAL —Kiln coal for the burning of white wares should 
contain about 62% of fixed carbon and 18% to 30% of 
volatile and combustible matter, and no greater than 6% 
moisture, 7% of ash and less than y 2 % of sulphur. Bitu¬ 
minous coal has 660 B.T.U. per cubic foot of coal gas, as 
compared to 1000 B.T.U. for natural gas and 150 B.T.U. 
for producer gas. The use of coal for the firing of clay- 
ware kilns requires more skill and more careful handling 
than any other fuel, and the atmospheric condition of kiln 



Ceramic Dictionary 


23 


firing under coal is in a continuous state of irregular 
vacillation, even under the best care and attention. 

COAL GAS —Gas given off from burning coal. Contains 
40% methane and 46% hydrogen, as compared to 92% 
methane in natural gas. 

COBALT —Used in ceramic bodies as a whitening agent 
either in the form of the very finely ground insoluble 
Cobalt Oxide, added directly to the body mix, or as the 
soluble crystalline Cobalt Sulphate added to the water 
which is retained from the filter press and used over and 
over again. The Sulphate does not cause blue stains 
common to Oxide practice. 

CO-EFFICIENT OF EXPANSION— The ratio of the 
increase of length, area, or volume of a body for a given 
rise in temperature to some other length, area or volume 
respectively. . • 

COHESION —The sticking together of all particles of a 
mass, whether the particles are all alike, or all unlike. 

COLLOIDS —The supposed fundamental of plasticity. Col¬ 
loids have a glue like gellatinous nature. Not crystalline. 

COLLYRITE— A hydrous silicate of alumina, of a compo¬ 
sition similar to clay, but not a clay, though having a clay 
like nature. 

CONCRETION— A mass of mineral matter formed in a 
rock or clay or earth, different from itself. Lime concre¬ 
tion are common in clays and iron oxide concretion in 
sandstones. 

CONE —The stack of a kiln. 

CONES —Pyrometric measures of heat established by Segar 
and made from ceramic materials the same as a body. 



24 


Ceramic Dictionary 


CONCHOIDAL —Having a shell like nature or fracture. 

CONTINUOUS KILN —Compartment or tunnel kiln, in 
which all or some portion of the fire is continually burning. 

CONTINUOUS MILL —A grinding mill usually having a 
hard porcelain lining and using hard pebbles as the grind¬ 
ing element, in which the product to be ground is fed into 
one end, and is discharged at the other end in the desired 
pulverant condition, without stopping the rotation of the 
mill. 

CONTRACTION —Normally accepted white ware ceramic 
clays and bodies should have a contraction in firing to 
cone 9 of approximately 12%. Amounts more or less than 
this to any appreciable extent are treacherous, except in 
Ball Clays, where full allowance is made. 

COOKING WARE— Two common varieties. The one 
using a common red body clay, one fire with a soft heavy 
white easily crazable glaze. The other of hard porcelain 
like body, high fire and covered with a hard impermeable 
glaze. 

CORNISH STONE —Same as Cornwall Stone. 

CORNWALL STONE —Cornish Stone, or China Stone, is 
partly rotted feldspathic rock. Used as a flux. Its for¬ 
mula is about 73% Silica, 18% Alumina and 7.5% Alka¬ 
lis. A more active fluxing agent than formula would in¬ 
dicate. The great value of the natural refined product 
to the potter lies in its mechanical qualifications as a sta¬ 
bilizing element in bodies. Artificial Synthetic Cornwall 
Stone has no value, as it lacks the natural mechanical 
qualities. 

CORUNDUM —A hard crystalized alumina used as an 
abrasive. 



Ceramic Dictionary 


25 


COULAGE —Casting process. 

CRAWLING —Same as Creeping, Jumping and Butterfly, 
in which the glaze may run or draw up to certain portions 
of ware leaving certain other portions dry, insufficiently 
glazed, and rough. 

CRAZING —Unequal expansion and contraction of body 
and glaze in which the glaze contracts more than the 
body. The remedies for this is first see that both body 
and glaze have sufficiently full fire. If this does not cor¬ 
rect the trouble then increase the flint in the body, or 
secure finer ground materials, or increase the feldspar in 
porous bodies, and decrease it in vitrified bodies, or in¬ 
crease the Ball Clay and decrease the China Clay. Or if 
desired in the glaze, reduce the Alkalis and increase the 
Flint, or increase the Boric Acid. 

CREEPING —Same as Crawling, Jumping and Butterfly, 
in which the glaze may run or draw up to certain por¬ 
tions of ware, leaving certain other portions dry, insuffi¬ 
ciently glazed, and rough. 

CREAM COLOR— “C. C.” Ware. The first name used 
for earthenware in 1725. Wedgewood afterward called 
it “Queensware.” C. C. ware today is semi-porcelain 
body, though of heavy coarse design similar to white 
granite. 

CRISTOBALITE —A crystalline form of silica derived 
from the heating of quartz. There are two modifications 
of cristobalite, namely—the alpha and the beta form, the 
former being stable below 225° C. and the latter above 
this point. 

CROCKERY —A general term for common earthenware. 



26 


Ceramic Dictionary 


CROWFOOT —Cracks, of this general design, formed on 
the surface of certain terra cotta or other wares, having a 
grog ingredient, so that glazing over the crack also runs 
in and assumes this same formation. The remedy is a 
finer grinding of grog, and care to secure no coarse par¬ 
ticles. 

CROWN —The arched roof of a kiln. 

CRYOLITE —A sodium aluminum flouride, used in manu¬ 
facture of glass. A material from Greenland. 

D 

DIABASE —Diorite rocks containing triclinic teldspars of 
a variety of compositions. 

DIATOMACEOUS —Infusorial earth. 

DIORITE —A granular crystalline igneous rock usually 
of soda-lime feldspar, containing the usual feldspar im¬ 
purities of biotite and quartz. 

DECALCOMANIA —Process of transferring designs from 
paper to pottery ware. 

DECREPITATION —Crackling. 

DEFLOCCULATE —The process of breaking up the ag¬ 
gregate particles of clay into finer ones, by the action 
of alkalis or the hydroxides of the alkaline earths. Usu¬ 
ally the carbonates of the alkalis or the silicates of the 
alkalis are employed, but the hydroxides of soda or 
potash may also be employed for this purpose. The re¬ 
sult of the deflocculation is a decided increase in the 
fluidity of the slip. Hence a fluid clay slip may be ob¬ 
tained with but little more water than the body has 
in the plastic state, without the presence of the alkaline 
electrolytes. As a rule the change from the undefloc- 
cuated to the deflocculatcd state is a sharp one, taking 



Ceramic Dictionary 


27 


place at a definite concentration of the alkalis. An ex¬ 
cess of the alkaline reagents may cause a reversion from 
the deflocculated to the undeflocculated state. See Casting. 

DELLA ROBBIA —Luca—The famous Italian potting ex¬ 
ponent about 1400. The developer of many fine Italian 
Ceramic Products. 

DELAWARE CLAY —A clay of primary origin found in 
Delaware, having a very open silicious nature and in¬ 
ferior color. 

DENUDATION —The exposure of rock by removal of 
overburden, or erosion. 

DETRITION —A wearing away by rubbing or disintegra¬ 
tion. 

DETRITUS —The result of the natural unmolested dis¬ 
integration of rock. 

DEVITRIFICATION —The recrystallization of a body or 
glaze to its original constituent parts, or partially so. 

DEXTRINE —An agglutinative material used as a binding 
plastic element in some bodies, and will burn out. 

DIASPORE —A hydroxide of alumina. 

DIDIER MARCH —A continuous tunnel kiln of the open 
fire type using cars. 

DIPPING —That process of covering a biscuit body with 
a glaze by emersion in the liquid, either by hand or 
machine. 

DIFFUSSION —To spread about in all directions. To 
permeate. 

DISINTEGRATE —The breaking down of a structure by 
natural weathering or artificial means. 



28 


Ceramic Dictionary 


DOLOMITE —A calcium magnesium carbonate having the 
same theoretical use in potting as whiting. 

DOUBLE DECK KILN— A round periodic kiln having 
a superimposed chamber. For the firing of hard ghlost 
ware in the lower kiln at cone 12 and the hardening of 
biscuit ware in the upper chamber, from the exhaust 
heat of the lower, at cone .010. In general use for the 
manufacture of continental porcelain. 

DRESSING TOOL —A small sharp edged iron instrument 
of hardened steel for dressing the sharp glaze on w r are 
made by contact in burning with pins and stilts. 

DRESSLER KILN —A continuous tunnel kiln of the 
muffle type using cars. 

DRY —Insufficient glaze. 

DUST TILE —Tile made under pressure on a press using 
clay body in form of a moist dust. Tile made in this 
manner have 20% of air space after firing. 

E 

EARTHENWARE —The commonly accepted term for 
white ware products having a porous absorbent body and 
a soft lustrou lead glaze fired to cone 9 in biscuit and 
cone 5 in ghlost, using the best available raw materal 
and having very colorful artistic decorations, as a rule. 

EGG SHELL —Condition of glaze caused by incomplete 
vitrification, or caused by small bubbles which do not 
seal over. 

EGG SHELL CHINA —Any very thin translucent china. 

ELECTRICAL PORCELAIN —A hard porcelain for the 
handling of low tension wires, insulation and equipment, 
and usually made by the dust process, firing by one 
fire both body and glaze to cone 10. 



Ceramic Dictionary 


29 


ELECTROLYTE! —Compounds of sal soda, water glass, 
etc., used to secure alkaline clay slip and suspension 
for casting. See Casting. Any salt which when dissolved 
in water causes the solution to become a good conductor 
of electricity. 

ENAMEL —A very soft boric acid opaque glaze melted 
on a metal base. Certain heavy glazes are called enamels. 

ENGLOBE —A very thin opaque glaze used as a support 
for a second thicker one. 

ENCAUSTIC —Varieties of hard paving tile with plain 
or colorful designs. 

EPSOM SALTS —Magnesium Sulphate, used as a tem¬ 
porary remedy for the settling of glaze in glaze tubs. Can 
be added directly to the glaze tub, or ground with the 
glaze. 2 Oz. to 1000 Lbs. of batch weight is the pro¬ 
portion used. 

EUTECTIC —The lowest possible temperature at which 
a combination of two or more materials melt. 

F 

FAIENCE —Ware having a very good body, as a rule, 
though not always, but always richly decorated and 
colorful. 

FAT CLAY —A rich plastic Clay. 

FELDSPAR —An aluminum silicate with either potassium, 
sodium, lime, barium or mixtures of all or any. Is an 
essential constituent of nearly all crystalline rocks. Feld¬ 
spar is of many varieties, but for potting only the ortho- 
clase feldspar should be considered as its coefficient of 
expansion better harmonizes with most body and glaze 
material, and for this reason has a greater margin of 
safety, and also easier controlled. Soda-potash feldspar, 





30 


Ceramic Dictionary 


anorthoclase feldspar is commonly called soda feldspar. 
It has a limited use in potting where it can be under¬ 
stood and made to fit. Feldspar is used in glass making 
to strengthen the glass by decreasing the brittleness 
and increasing the toughness. It also may be an aid 
to quicker setting of the glass under certain conditions, 
thus speeding up production. Commercially speaking 
there is no perfect feldspar. The formula for such were 
it found would be— 

Silica .65. 4% 

Alumina .18. % 

Potash .16.60% 

This is perfect orthoclase pottery feldspar. In nature 
it does not exist. Feldspar is also spelled Feldspath, 
Felspath and Felspar. 

FELSITE —A dense very fine grained igneous rock con¬ 
sisting almost entirely of feldspar and quartz in very 
fine crystals. 

FERROUS —Containing iron, or its compounds in any 
form. Iron bearing. 

FERRUGINOUS —Containing iron, or its compounds in 
any form. Iron bearing. 

FILTER PRESS —A machine for the removal of water 
from clay slips, or clay bodies, using bags. 

FIRE BOX —That portion of a kiln where the kiln fires 
are burned. With coal it contains the grates and the 
coal. With oil and gas it is an open chamber where 
the flames originate. The fire boxes are usually built 
in the kiln, but not always, as sometimes they are 
separate outside boxes. 

FIRE CLAY —A refractory earth capable of resisting the 
action of high temperatures without change of form 






Ceramic Dictionary 


31 


under pressure. A true fire clay should be a very pure 
form of natural ciay and very free from alkalis and 
should not melt below cone 26. 

FIRING —Or burning. That process of heat treatment 
of all ceramic products, for the purpose of securing re¬ 
sistance and permanency of product; the fluxing of glazes 
or the hardening of decoration. It is the most important 
single phase of all ceramics. See Kiln Firing. 

FLASHED —Ware which has come in direct contact with 
the flame causing an irregular discoloration, usually of 
a reddish brown color. 

FLASHED GLAZING —A manipulation of colored glazes 
in imitation of fire effects. 

FLINT —Silica—Oxide of Silicon, is of four varieties for 
ceramic purposes. Sand Flint, Quartz Flint, Amorphous 
Flint and French Flint. It is the principal opening ma¬ 
terial in ceramic bodies and the principal non-plastic 
element. All ceramic flint should not only run over 
99% pure, but should contain no appreciable quantity 
of lime, or a variable quantity of it. The grinding of 
flint for the majority of ceramic products is 140 mesh, 
though some products require 160 mesh or finer. For some 
products Flint can be used too fine so as to lose the 
effect of an opening material, and cause other trouble. 

FLINT GLASS —A glass made from sand with a com¬ 
bination of lead, potash or soda. Usually for table use. 
Also called crystal ware. 

FLOCCULATE —The reverse of deflocculation, in which 
the clay particles are caused to form larger aggregates 
by the addition of acid or salts, which counteract the 
function of the alkalis. The flocculating action of salts 
is stronger the higher the valency of the basic element 
involved. 



32 


Ceramic Dictionary 


FLORIDA CLAY —A highly refined white burning residual 
clay of conchoidal nature having fine grain and char¬ 
acteristics of both ball and china clay. 

FLOURSPAR —Calcium Flouride. Not a ceramic product. 

FLOW —A mixture of saltpeter, borax and white lead 
placed in saggers during ghlost fire to cause colors to 
flow or become softer in texture. 

FLOWN WARE —Cracked ware. 

FLUE —An enclosed passageway for controlling and di¬ 
recting the passage of air or gas. 

FLUX —To become fluid. The common body flux is feld¬ 
spar, although vitreous ball clays may act also to a 
certain extent in this capacity, dependent upon the state 
of vitrification. These fluxes melt, become fluid, and 
on cooling harden again and form a binding element, 
and an amalgamation of associate particles. Glaze fluxes 
are Feldspar, White Lead, Borax, Boracic Acid, Zinc 
Oxide, and Tin Oxide. Paris White is a fluxing agent 
only in contact with other material. 

FORMATION —Water of formation is that water required 
to mix with a clay body to render it workable. 

FOOT —A unit of length. 

FRANKSTONE —Same as Barium Carbonate. 

FRENCH FLINT —Silica made from hard French or 
Danish pebbles found water washed on the coast of 
those countries. Is of an amorphous nature and likely 
to contain certain percentages of lime. 

FRIT —The process of rendering soluble material insoluble, 
in which the soluble ingredients of a glaze are melted 
to form insoluble silicates. 



Ceramic Dictionary 


33 


FUCHSLNE DYE —In wood alcohol under a pressure 
of 200 Lbs. is the most severe test for penetration for 
porosity and absorption. A body which permits no pene¬ 
tration of this test may be considered perfect amalga¬ 
mation and vitrification. The dye is made by dissolving 
3 Oz. of fuchsine crystals in 10 Gal. of alcohol. For 
ordinary commercial practice this test is much too severe 
for commercial bodies, as very few if any, clay bodies 
will be sufficiently vitrified and glass like to permit no 
penetration. 

G 

GABBROS —Any of a very large family of igneous rocks. 
Composed essentially of various forms of plagioclase 
feldspars. 

GAS ANALYSIS —With the cost of kiln fuel constantly 
advancing, the daily use of an apparatus for gas analysis 
in testing the waste gases from the kilns would prove 
a valuable means of detecting inferior firing and serve 
as a guide for the more accurate and economical use 
of fuel. 

GASEOUS FUELS —Gases have a wide variety of formula 
and value as follows: Natural Gas has a heat value of 
1000 B. T. U. per cubic foot. Oil Gas 846, Coal Gas 660, 
Coke Oven Gas 603, Water Gas 295, Producer Gas 144. 
A thousand feet of Natural Gas will evaporate 893 Lbs. 
of water, Coal Gas 591, Water Gas 262, and Producer 
Gas 115. Natural Gas contains 92% Methane, Oil Gas 
48%, Coal Gas 40%, Water Gas 2% and Producer Gas 
2%. Natural Gas contains 3% of hydrogen, Oil Gas 32%, 
Coal Gas 46%, Water Gas 48%, and Producer Gas 10%. 
Nitrogen is the principal ingredient of Producer Gas, with 
Carbon Monoxide 25%, and Water Gas is 38% Carbon 
Monoxide. 



34 


Ceramic Dictionary 


GAS WASTE— See Gas Analysis. 

GEORGIA CLAY— A light buff or cream colored clay 
of very fine grain of secondary nature, usually found 
remarkably free from ordinary primary clay impurities, 
but usually containing other impurity. Titanic Oxide 
is the principal impurity. 

GIBBSITE —A hydroxide of alumina, light colored and 
translucent. 

GIOBIRITE —A substance of a clay like nature, some¬ 
times used as a refractory. 

GLASS —An artificial amorphous fabricated substance, usu¬ 
ally translucent, made from some form of silica, or sand 
fused with a large content of alkali, and with potash, 
soda, lime, borax or lead or other material. Also colored 
with other metallic oxides. 

GLAZE —Literally a glass. A covering for ceramic wares 
in order to secure greater permanency and beauty of 
product. White ware glazes may be glass, but in glaze 
making it is preferable to use materials similar to body 
as far as possible in order to secure a similar coefficient 
of expansion. White glazes are of two classes, hard 
and soft. The hard glaze may be a high fire calcined 
silicious feldspathic lime mixture, very hard and resis¬ 
tant. Soft glazes may be of lead and borax and easily 
scratched. The white glazes are most difficult to pro¬ 
duce, as they usually cover articles of use and wear. 
Colored glazes and matt glazes are usually of a soft 
texture and offer many varieties of composition, beauty 
and application. 

GLAZE RUNS —Should a glaze run from the surface of 
dense hard wares in the dipping process, this action 
may be retarded by the addition of a little vinegar to 



Ceramic Dictionary 


35 


the glaze tub which acts on the lime. The addition of 
a little raw borax diluted in warm water added to tub 
may also retard this action. 

GNEISS —A metamorphic rock, having a composition simi¬ 
lar to granite or other feldspathic rock, but having its 
parts especially mica, arranged in planes so that it splits 
easily into irregular slabs. 

GOLD —Used extensively in decoration of ceramic products 
in three forms. Pure coin gold and liquid bright gold, 
and dilutions of both. The former made by a very care¬ 
ful and intimate grinding of pure gold, quicksilver and 
flux. The bright gold is a dilution by reduction. Gold 
is- usually the base color for the production of fine ox 
blood red glazes. 

GRAM— A unit of weight. 

GREEN WARE —Finished clay ware, yet unburned. 

GROG —Calcined sagger or terra cotta, constituent made 
from carefully ground and well lawned old fired saggers. 
It usually forms 50% of sagger mix and is used in varied 
proportions in terra cotta, and other heavy clay products. 

GYPSUM —Calcium sulphate. The mineral from which 
plaster of paris is made. 

H 

HALLOYSITE —A silicate of alumina of an amorphous 
nature, Clay • like, but not true clay. Texas clay is a 
well known variety of this. 

HARDNESS —The hardness of a material is expressed 
in terms of the following: Standardized scale—1, Talc. 
2, Gypsum. 3. Calcite. 4, Flourite. 5, Apatite. 6, Feld¬ 
spar. 7, Quartz. 8, Topaz. 9, Sapphire. 10, Diamond. 



36 


Ceramic Dictionary 


HARDENING ON— That process of burning on or in 
of an underglaze decoration in the decorating kiln, about 
700 C, and the burning off of the size and oil, in order 
to apply the glaze. 

HARDINGE MILL— A cone shape continuous feed and 
discharge pulverizing mill. 

HARD PORCELAIN —White porcelain made under very 
high fire as a rule, cone 12-16, vitreous, transparent and 
non-absorbent and very resistant, and using clay, feldspar 
and flint as principal ingredients. Also called natural 
porcelain. 

HEATS —Potting heat of various commercial practice are 
as follows: American Earthenware, cone 9 in bisque 
and cone 6 in ghlost. American Vitrified China, cone 
11 in bisque and cone 7 in ghlost. English Earthenware, 
cone 4 in bisque and cone 2 in ghlost. English Vitrified 
China, cone 10 in bisque and cone 8 in ghlost. Conti¬ 
nental Porcelain, cone 010 in bisque and cone 12 in 
ghlost. 

HEMATITE —A form of iron oxide found in many com¬ 
mon clays, which burn reddish brown, brown, or other 
dark brown colors. Brown Hematite is also called 
Limonite. 

HIGH TENSION PORCELAIN— Hard, one or two fired 
articles made by casting, dust or wet process for the 
handling of electrical lines and wiring of high voltage. 
The product is non-absorbent, free from pores and metal¬ 
lic oxides and of great strength. Cone 10 is usual fire. 

HILLIERS —A cap for a bung of ware, or a cap for a 
sagger, made from the same material and the same 
shape as the sagger. 



Ceramic Dictionary 


37 


HORNBLENDE —A silicate of calcium and magnesium 
with one or more other metals as iron, manganese. 
Common to many crystalline rocks. Also called 
Amphibole. 

HUMOUS —Containing a relatively large amount of hu¬ 
mus. Humous substances in solutions are important 
solvents of rocks. 

HUMUS —Partially decomposed animal or vegetable 
matter. 

HYDROGEN —With carbon-monoxide the principal in¬ 
gredient of water gas. 

HYDROSCOPIC WATER —Mechanical water capable of 
being measured in a substance by the hydroscope. 

HYDRARGILLITE —A hydroxide of Alumina. Light 
colored and usually translucent. 

HYDROUS —Containing water in chemical combination. 

HYGROMETRIC WATER— That moisture a body or 
substance will absorb from the surrounding air depend¬ 
ent upon the atmospheric humidity. Certain materials, 
like Ball Clay, have a strong hygrometric nature in ab¬ 
sorbing moisture from the air, or easily releasing it by 
evaporation. 

HYGROSCOPIC WATER —The water contained in dry 
clay which has not been heated above 75° C. It is also 
the water which may be absorbed by dry clay when ex¬ 
posed to the atmosphere. Ball Clays, for example, have 
a strong hygroscopic nature in absorbing moisture in 
damp air, and easily releasing it in dry air. Ball Clays 
may absorb as high as 15% moisture in damp air. Al¬ 
most all materials, however, have some hygroscopic 
nature. 



38 


Ceramic Dictionary 


I 

IGNEOUS— Containing fire. Rocks resulting from, or 
produced by, the action of intense heat. Granite and ba¬ 
salt are igneous rocks. 

ILMENITE —An iron-black mineral, having a sub-metal¬ 
lic lustre. It is a compound of iron, titanium and oxy¬ 
gen, and is common impurity in some sands. 

IMPURITIES —In all ceramic material, whether refined 
or unrefined, there may be found two classes of impurity. 
One, natural impurities, and the other foreign impurities. 
Natural impurities most likely to be found in refined cer¬ 
amic materials are the same as those found in the crude 
material, from which the refined is made, as it is not 
always possible to completely purify. A flint deposit in 
the crude state may contain some vegetable iron, and 
perhaps some lime, so likewise, in the refined flint, these 
same impurities are most likely to be found. These are 
natural impurities. In feldspar these are most likely to be 
black and white mica, free quartz and various forms of 
iron, as these impurities naturally are found in feld- 
spathic rock. In primary china clays the impurities most 
likely to be found are the same as in feldspar, as both are 
formed in nature from the same rock. In secondary resid¬ 
ual china clays the same impurities are likely to be found 
as in the primary, but there is also likely to be found 
foreign impurity due to contamination during water trans¬ 
portation. That is, impurity introduced from the outside. 
In secondary clays there is less likely to be found nat¬ 
ural impurity, or much of it, as the natural water classir 
fication purifies most of it. Cornwall stone is most likely 
to have the same impurity as feldspar and primary china 
clays, as this comes from the same rock. Paris white may 
have some free silica or iron. Whiting likely to contain 


j 




Ceramic Dictionary 


39 


excess quantities of magnesia, free silica, or iron com¬ 
pounds, or in the by-product whiting, sulphur or othei 
chemicals. In ball clays the natural impurities are most 
likely to be compounds of iron or a superabundance of lig¬ 
nite and carbonaceous matter, although small amounts 
of the latter are allowable. Almost any impurity destroys 
the value of high grade fire clays, though iron pyrites may 
be found. White lead, tin oxide, borax and acid, in these 
very little impurity of any kind should be found. These 
are glaze materials, and they should be purchased on their 
basis of great purity, as impurities in these materials dis¬ 
color the glaze'. Impure white lead will tint the glaze a 
yellow, and impurities in other products cause a tint of 
color. Foreign impurities, or foreign matter, or unnat¬ 
ural impurities are those which are introduced into the 
material from any other source not found in the original 
crude material. 

INFUSORIAL EARTH —The silicious remains of minute 
organisms, animal and vegetable, usually found in low 
country. Used as a ceramic ingredient sometimes, but 
mostly as an abrasive. 

INORGANIC —Not organic. Composed of, or pertaining 
to, all matter outside animal and vegetable kingdoms. 
Metals, Clays, Flints, Lead, etc., are all inorganic com¬ 
pounds. Coal and gas are organic compounds. 

INSOLUBLE —Not capable of being dissolved in hot or 
cold water. 

INSULATION —Insulation of ceramic kilns to prevent 
unnecessary loss of heat through undesired radiation is a 
subject of great concern to the potter, and each particu¬ 
lar kiln must be treated for this as a separate unit. Too 
much insulation is likely to result in the burning out of 
interior parts. 



40 


Ceramic Dictionary 


INTAGLIO— Cut in, in depressed design. Opposite to 
Cameo. 

INTERSTITIAL —The spaces between particles of a mass. 
A piece of porous ware will absorb 15% of water. This 
water is held in the interstitial spaces of the body. Vit¬ 
reous ware has no interstitial spaces and so has no power 
of absorption. 

INTERMITTENT KILNS— Periodic. Those filled, fired, 
cooled, and the process regularly repeated. 

IRON —Usually the least dangerous of all ceramic impur¬ 
ity in refined material, as it is the most easily detected 
and controlled. This is even true of non-magnetic or 
vegetable iron, as should there be much of the latter, there 
usually is an abundance of magnetic iron also, which aids 
the detection. Iron and its compounds ruin more pos¬ 
sible ceramic material than any other impurity, but this 
is usually detected at the source, although some form of 
iron even in small traces can be found in all ceramic 
material. 

J 

JAW CRUSHER —A heavy mechanically operated crush¬ 
ing device, having jaws which open and close for the pur¬ 
pose of preliminary crushing of material prior to selec¬ 
tion and final pulverization. The jaws are of phosphor- 
bronze, or phosphor-manganese. 

JELLYTONE— An ice cream product used to thicken glaze 
in a glaze tub. A temporary remedy. 

JET WARE —Usually a red clay body covered with a blue 
glaze producing a black jet. 

JIGGER— A machine for making round or oval clay prod¬ 
ucts. 

JOLLY —Same as Jigger. 




Ceramic Dictionary 


41 


JUMPING —Same as Creeping, Crawling and Butterfly, in 
which the glaze may run or draw up to certain portions 
of ware, leaving certain other portions dry, insufficiently 
glazed, and rough. 

K 

KAOLIN —China Clay. From the Chinese word Kao- 
ling, meaning high hill, and meaning a good quality white 
burning clay. 

KAOLINITE —Same as Kaolin or China Clay, but always 
refers to the crystalline, or almost pure form. 

KERAMICS —Same as Ceramics, as occasionally used by 
the Art and Decoration Side of Ceramics. 

KICKWHEEL —Potters wheel manipulated by the feet of 
the user of the wheel, in which the thrower forms the 
ware by hand, and furnishes the power by his feet. 

KILNS —There are ten distinct types of commercial pot¬ 
tery kilns in use. 

1. —Round Periodic Kilns, up draft. 

2. —Round Periodic Kilns, down draft. 

3. —Round Periodic Kilns, double decker. 

4. —Horizontal Periodic Kilns, one fire hole. 

5. —Horizontal Periodic Kilns, many fire holes. 

6. —Muffle Periodic Kiln. 

7. —Continuous Kilns, one fire hole. 

8. —Continuous Kilns, many fire holes. 

9. —Continuous Tunnel Kiln, muffle type. 

10.—Continuous Tunnel Kiln, open fire type. 

KILN GASES —The composition of kiln gases not only 
varies with different fuels and conditions, but varies in 
same kind of fuels, using the same kind of kiln of same 
size. All firing is done in four possible types of atmo¬ 
sphere—oxidizing, neutral, or reducing, or all. Oxidizing 



42 


Ceramic Dictionary 


is when there is an excess of air over combustible gases. 
Neutral is when the kiln atmosphere contains neither an 
excess of combustible gases or air. Reducing is when 
there is an excess of combustible gases over air. Most 
wares require firing in oxidizing atmosphere, some neu¬ 
tral, and some reducing, but in periodic kilns all four con¬ 
ditions are likely to be had during the firing process, 
though only one desired, particularly is this true using 
coal for fuel. The atmosphere of a kiln may be alter¬ 
nately oxidizing and reducing, and especially is this true 
at the higher temperatures, harder to control. In vit¬ 
reous ware and glazed wares the color corresponding to 
the composition of the kiln atmosphere surrounding that 
ware at the time of vitrification or fusion, will be defi¬ 
nitely retained by the ware. Coal smoke may cause a 
yellow tinge to vitreous wares, but not as a rule to por¬ 
ous wares. Coal gases are usually acid, and likely to 
form sulphuric, sulphurous or hydrochloric acid fumes in 
the kiln which act on the basic elements, such as the lime, 
potash and soda in the glaze with injurious effect—the 
source of some kiln scumming. Kiln gases may be oxy¬ 
gen, hydrogen, nitrogen, acid fumes, steam, carbon-diox¬ 
ide, carbon monoxide, or other hydro-carbons. See Gas 
Analysis. 

KILN FIRING —There are five distinct stages of kiln fir¬ 
ing. 1st stage—Water smoking, in which all mechan¬ 
ical and chemical water is driven off from the product. 
This stage is from the time the kiln is first lit up to 700° 
Cent., or cone 018. The greatest shrinkage occurs in this 
period. 2nd—Firing period, in which the constituent ma¬ 
terials readjust themselves to heat advances, and at the 
end of this period chemical combinations of flint, clay and 
spar begin to form silicates. 3rd—Softening period, in 
which first symptoms of vitrification and melting begin. 



Ceramic Dictionary 


43 


4th—Soaking, in which the heat desired is held without 
further advances, so as to allow it to soak in and ma¬ 
ture all portions of all ware in all remote parts of the 
kiln. 5th—,Cooling period, in which the soft mass be¬ 
comes hard and cools. In continuous tunnel kiln work 
this same condition prevails, except in zones of the kiln, 
all five periods going on at once. 

KILN STRUCTURE —May be of any kind of resistant 
material, any size or design, all dependent on the product 
to be made, method of making and heat to be used. 

KING-TE-CHEN —The famous pottery town of China of 
300,000 population, entirely devoted to potting. 

L 

LABRADORITE —Soda-Lime Feldspar. 

LAPIDOLITE —An easily fusible glass constituent having 
a formula of: silica 47.61, alumina 23.36, potassium 16.16, 
lithum 4.91, soda .38, magnesia .64, and containing un¬ 
certain quantities of manganese, which spoils it for a 
pottery material. 

LATERITE —A porous, usually reddish, clay formed by 
decomposition in certain rocks, usually in tropical re¬ 
gions, consisting mainly of hydrargillite, not like ordi¬ 
nary clay. 

LATERITIOUS —Like bricks. Of the color of red bricks. 

LAZULITE —Blue spar. A hydrous phosphate of alumina. 

LEACHING —The dissolving of a material, or certain por¬ 
tions of it by the action of water draining or percolating 
through it. 

LEAD— In ceramic practice usually as white lead, or lead 
carbonate, containing 86.6% lead oxide and 13.4% carbon 
dioxide gas. Its value in ceramics is its purity. In lead 



44 


Ceramic Dictionary 


glazes care must usually be taken in kiln firing to avoid 
reducing temperatures for any length of time, as the com¬ 
bustion gas seeking oxygen steals it from the lead oxide 
leaving metallic lead, which blackens the glaze. Red lead 
is lead tetroxide used sometimes in ceramics as a sagger 
wash, and in some frits, but extensively used in the glass 
industry. 

LEAN —The condition of any material not plastic, or not 
very plastic. 

LENZENITE —A clay like material, similar to Halloysite. 

LENSES —Limited occurrences of mineral matter due to 
the localized action which caused the material to be 
formed. 

LEVIGATE —To stir in water so as to separate the coarse 
particles from the fine. To wash and purify substances 
by water separation. 

LIGNITE— A variety of coal still showing the wood struc¬ 
ture, of recent origin. 

LIMONITE —A hydrous ferric oxide. It is the usually 
coloring matter of yellowish brown rocks and clays. Also 
called Brown Hematite. 

LITHARGE —Lead monoxide. Not used in ceramics as 
such. A glass ingredient. 

LOADSTONE —Magnetite, an oxide of iron possessing 
polarity like a magnetic needle. Sometimes found in 
sands and clays and strongly attracted by the magnet. 

LOAM— A clayey earth, or any earth or soil. A clay loam 
or a sand loam denote an excess of these. In general use, 
loam implies a presence of considerable portion of de¬ 
composed organic matter. 

LUSTRE —Luster. A pearl, silky, iridescent sheen, or glass 
like surface. 



Ceramic Dictionary 


45 


M 

MANGANESE —A strong coloring agent. In any of its 
forms is an impurity in clay products. 

MAGNESIA —Magnesium carbonate. A common constit¬ 
uent of almost all ceramic material in limited quantities. 

MAGNESITE —Magnesium carbonate sometimes used in 
ceramics as a body ingredient, though with strong tend¬ 
encies to crack, due to its cement like nature, unless 
calcined. 

MAGNETITE —An oxide of iron. Occurring in sands, 
clays and earths. It is attracted by a magnet. Also called 
Loadstone. 

MAJOLICA —A highly lustrous or colorful opaque glazed 
pottery product, having a soft open porous body usually 
of inferior clays. Also called Majurca. 

MARBLED WARE —Ware in imitation of marble. 

MARGIN OF SAFETY —An important factor in the pro¬ 
duction of any body or glaze, for the manufacturing and 
commercial success of the plant. Many bodies and 
glazes are too sensitive to variations in kiln fire which 
is not necessary, and which could be remedied. A glaze, 
for example, which matures nicely at cone 9, but which 
would remain partially unfluxed at cone 7, or even cone 
8, would be too sensitive for ceramic practice on a large 
commercial scale. The margin of safety is too narrow. 
Any glaze or body which would show wide variations in 
appearance or structure at the probable variations in com¬ 
mercial kiln firings is operating on too narrow a margin 
of safety. Opaque glazes may carry a certain proportion 
of an opacifying agent which would act beautifully at 
cone 8, but tend to blister at cone 9. Therefore, the pro¬ 
portion of this agent being carried in the glaze is not cor- 



46 


Ceramic Dictionary 


rect in proportion to the other ingredients, thus causing 
the glaze as a whole to have too narrow a margin of 
safety. In most commercial practice such narrow mar¬ 
gins of safety are not necessary, and only exist due to 
lack of knowledge, experience, or energy required to 
change them. 

MARL—A rich limey earth. 

MARLOW KILN—A continuous open fire tunnel kiln, 
using cars which are pulled, not pushed. 

MAULING—The wedging of masses of prepared clay by 
means of beating with heavy wooden flat headed mauls. 
This process is used for the 'removal of air spaces or 
cracks in clay masses, so as to prevent or retard the ac¬ 
tion of drying out, and to aid colloidal degeneration. Pre¬ 
pared made clay in masses for the purpose of storage in 
order to secure aging desired, should always receive this 
preliminary treatment as the piles are built up, so that 
each clay pile is a fairly homogeneous clay mass, free 
from large air spaces. This process also renders large 
volumes of clay more uniform in water content. 

MECHANICAL ANALYSIS—A study of the structure of 
a substance. A very important- branch of ceramic knowl¬ 
edge. In many cases a mechanical knowledge of cera¬ 
mic material is of greater significance than chemical 
knowledge. 

MECHANICAL WATER—Water of formation, pore 
water, or hydroscopic water, or any water capable of lib¬ 
eration from a body heating at 120° C. Water not chem¬ 
ically combined. 

METAMORPHISM—A change of physical structure. In 
rocks and earths brought about by disintegration and 
re-formation. 



Ceramic Dictionary 


47 


METHANE—A gaseous hydrocarbon. The principal in¬ 
gredient of natural gas and one of the ingredients of coal 
gas. 

MICA—A mineral common to all feldspathic rocks and 
clays. Tough and elastic, and the different varieties, com¬ 
posed of many compounds, are all silicates. Ismglass is 
a transparent mica. Biotite and Muscovite are common 
to ceramic material, though all varieties may appear in the 
same rock. Mica is a very undesirable substance in pot¬ 
ting products as it fuses with great difficulty, is an anti¬ 
plastic, and its presence in a body destroys cohesion both 
before and after firing. 

MICROLINE—A potash feldspar, but triclinic in form. 
Could be used for a pottery feldspar, but not found in 
sufficiently abundant deposits. 

MICRO-ORGANISM—Any organism of a microscopic 
size. Bacteria. 

MOISTURE—All ceramic material has some hygrometric 
nature, and all will absorb and liberate certain amounts 
of water from the air, dependent upon the humidity and 
the material. Some materials may absorb only 2% of 
moisture under very wet atmospheric conditions, while 
others may absorb 9 % under the same conditions. Dry 
ground nlaterials will never absorb as much moisture as 
water ground. 

MOLD—The plaster of paris form, on or in which pot¬ 
tery ware is made. 

MONOCLINIC—Having an oblique intersection of the 
axes. Refers especially to the crystalline form of com¬ 
mon, or orthoclase feldspar. 

MORTAR—Mortar for the building and repairing of kilns 
is best made from ground or pulverized fire clay of fine 
quality, and allowed to stand forty-eight hours mixed w r ith 



48 


Ceramic Dictionary 


water before use. Cheap mortar, made from cheap, or 
low grade fire clays, is poor economy. The best is none 
too good. 

MOSAIC—Consisting of small pieces of glass, tile or other 
material to form a design, usually colorful. 

MUFFLE—A compartment for baking ware without ex¬ 
posing the contents to the direct action of the flames. 
Firing by muffle is firing by radiation. 

MUSCOVITE—White mica common to all clays and feld¬ 
spars. May also be yellow or brown, but always pearly. 
Is a complex silicate with potash, and is known as com¬ 
mon mica. 

N 

NATURAL GAS—The most efficient fuel. Contains 92% 
methane and has 1000 B.T.U. per cubic foot. One thou¬ 
sand cubic feet will evaporate 893 lbs. of water. See 
Gaseous Fuels. 

NATURAL PORCELAIN—Porcelain made from clay, 
feldspar and flint as the principal ingredients. Also called 
Hard Porcelain. 

NEUTRAL HEAT—Kiln conditions which are neither oxi¬ 
dizing or reducing, in which there is no surplus air, or 
gases of combustion. 

NITROGEN—The principal ingredient of Producer Gas. 
Air is about 78% nitrogen. 

NON-ABSORBENT—Many wares are sold as non-absorb¬ 
ent, vitreous, or impermeable, such as porcelains, or wares 
of this type. The use of the word non-absorbent is only 
relative as there are very few wares with a clay body, or 
having clay for a base which are absolutely non-absorbent 
to all liquids. Commercially speaking, most of them sold 
as such are non-absorbent to water, or perhaps even red 



Ceramic Dictionary 


49 


ink, which would not be non-absorbent under the fuch- 
sine dye test. In other words, the use of such words in 
ceramics as non-absorbent, vitreous and impermeable re¬ 
lates to water penetration, unless otherwise specified. 

NON-PLASTIC—Any material not plastic or fat. In pot¬ 
tery the so-called non-plastics are flint, feldspars, paris 
white, whiting and some clays. 

NORTH CAROLINA CLAY—A primary clay of feld- 
spathic origin, having all the characteristics and impuri¬ 
ties common to primary clays and like such clays require 
considerable washing to purify. Is highly refractory, and 
its great value and function lies in its ability to aid cera¬ 
mic wares in keeping its shape during the firing period. 
About 15% is the usual percentage used. They have a 
wide range of color. Almost all of them are coarse 
grained. 

O 

OCTAHEDRITE—Titanium oxide. 

OHM—A unit of electrical resistance. 

OIL—See Petroleum. Engine oils are refined petroleums. 

OIL FIRING—The use of petroleum under air pressure at 
certain temperatures using certain types of burners for the 
production of heat. 

OLIGOCLASE—A soda lime feldspar of triclinic form. 

OLD PORCELAIN—Sold as such, but most of it repro¬ 
ductions, and impossible to detect even to the critical eye. 
The Chinese have been reproducing their old porcelains 
for centuries. Reproduced Old Porcelain is much supe¬ 
rior to the genuine in body composition, a most desira¬ 
ble situation. 

OPAQUE—Not transparent. Tin oxide is the common 
opacifying agent in white glazes. In colored glazes many 
oxides can be used, dependent on the color desired. 




50 


Ceramic Dictionary 


OPENING MATERIAL—Material used in plastic bodies 
to reduce shrinkage and to open them so as to reduce 
cracking and warpage. They are non-plastics, such as 
flint, or highly silicious lean clays, sand, compounds of 
lime, carbonaceous matter, sawdust, or calcined material 
as pulverized biscuit ware, or grog. In any white ware 
body true rock quartz flint, water ground, is the ideal 
opening material, but is seldom used on account of its 
high cost. 


OPTICAL PYROMETRY—The burning of ware in a 


kiln using 

the experienced eye as a judge in 

the deter- 

mination of temperature by the color of lhe 

flame, and 

the color of objects in the flame. A bar of iron on heat- 

ing assumes colors as follows 

: 


Yellow. 

.437°F. 

Indigo . 

....550°F. 

Orange. 

.473 

Blue . 

....559 

Red . 

.509 

Green . 

....650 

Violet . 

.531 

Grey . 

....752 

and following this the color of 

the flame itself, or the color 

of objects in 

the flame: 



Red . 

.1000°F. 

Dark Orange... 

.. .1994°F. 

Dark Red .. 

.1310 

Light Orange.. 

,...2174 

Cerise. 

.1472 

Bright White . 

....2354* 

Cerise. 

.1607 

Dull White.... 

...2534 

Bright Cerise 

.1814 

Shining White. 

... .2714 

♦Cone 9. 




ORGANIC- 

■Of an animal or 

vegetable source 

or nature. 


ORTHOCLASE—Potash-soda Feldspar. The only mono¬ 
clinic feldspar. All other feldspars are triclinic in form. Is 
common pottery feldspar. 

OVERBURDEN—Earth overlying a deposit of mineral, 
quarry stone or clay beds. Heavy overburdens are not 
only expensive to remove and handle, but in many cases 




















Ceramic Dictionary 


51 


actually handicap the quality of material sought. Where 
the overburden is too heavy the expense of mining may 
be so great as to actually prohibit continued mining oper¬ 
ations. 

OVERFIRED—To break down the desired structure of 
a body or glaze due to excessive heat. 

OWEN KILN—A continuous tunnel kiln of the open 
flame type, using cars. 

OX BLOOD—The most highly prized and difficult glaze 
color to secure in ceramics. Made with gold. 

OXIDE—Usually an element in combination with oxygen 
alone, but sometimes a combination of elements with 
oxygen. 

OXIDIZE—To join with pure oxygen or to join with the 
ox3'gen of water, or the air, or other oxygen compounds. 
When a metal rusts it oxidizes. 

OXIDIZING FLAME—-A flame sufficiently satisfied with 
air or oxygen so that all combustible gases are burned 
out leaving no waste uncombined gases. 

OXIDIZING FIRING—Firing with sufficient air so that 
there is an excess of air over combustible gases. 

P 

PALISSY—Bernard. The so-called French hero of cera¬ 
mics about 1539, who burnt his furniture in the firing of 
his last kiln in seeking to develop certain enamels. 

PLAGIOCLASE—Triclinic feldspars. 

PASTE—A hard setting paste to seal cracks or imperfec¬ 
tions in finished wares, without refiring the product, is 
Litharge mixed with a very pure, moisture free, gly¬ 
cerine. 

PARIAN—Unglazed soft porcelain in bisque, usually a 
very soft body, and used for art purposes. Non-plastic 
and body composed of about 60% stone and 40% feldspar. 



52 


Ceramic Dictionary 


PARIS WHITE—Calcium carbonate. Is usually 98% pure. 
Used as a flux or neutralizing agent in body and glaze. 
A very inert, inactive compound by itself, but vigorous in 
the presence of other ceramic silicates. It should be the 
most finely pulverized of all ceramic material, over 300 
mesh. In kiln is reduced to 56% calcium oxide, lime, 
and 44% carbon dioxide gas. The liberation of this gas 
in a body or glaze starts at 590° C. (Cone 022) and con¬ 
tinues until 990° C. (Cone 08), when the action is com¬ 
plete. If the material is not sufficiently finely pulverized, 
large particles give off large volume of this gas in one 
place, large bubbles, or bloating is very likely to occur in 
the body, or blisters in the glaze. (See blisters.) True 
Paris White comes from the Chalk Cliffs of England, and 
has an amorphous structure formed from shells, or shell 
like fragments, and is very easily pulverized. The re¬ 
sultant pulverized material has feather like edges, a qual¬ 
ity which enables it to remain in suspension a greater 
period of time than any other ceramic material, and on 
this account alone, an excellent glaze constituent. And 
on account of its fineness, also an excellent body material. 

PATE-sur-PATE—Decoration by painting layers of white 
slips on a colored body and chiselling out the design. 

PATE-TENDRE—Artificial or soft porcelain. 

PEBBLES—Hard amorphous water worn silica stones as 
found on the coast of France and Denmark. 

PEBBLE MILL—See Ball Mill. 

PEELING—Same as ruckling. 

PEGMATITE—A graphic granite feldspathic rock occur¬ 
ring in veins or dykes. 

PEPPER SPECK—The black speck common to feldspar 
or some clays is usually caused by Biotite Mica, but some¬ 
times by certain iron compounds. 



Ceramic Dictionary 


53 


PERIDOTITE—A large group of granetoid igneous rocks 
containing many varieties of minerals, but little or no 
feldspar. 

PERIODIC—Intermittent. Kiln burned at fixed intervals, 
not continuous. 

PETROGRAPHY—The study and classification of rocks. 

PETROLEUM—A complex hydrocarbon. The crude nat¬ 
ural liquid mineral used for heat. Has a boiling point of 
about 80°. Pennsylvania varieties have a paraffine base 
and will run 60-68% gasoline. Texas and Mexican va¬ 
rieties run 28-38% gasoline and usually with an asphal- 
tum base. Ohio and Canadian varieties are likely to con¬ 
tain sulphur. 

PETUNTZE—Chinese feldspar. In the same category as 
Cornwall Stone. 

PHOSPHATE PORCELAIN—Ware made using ground 
bones as an ingredient. The shin bones of the ox being 
preferable. 

PINS—Various sized burned fire clay supports on which 
dipped ware rests during the ghlost firing period to avoid 
contact. The point of contact is usually on the under 
edge. 

PIN MARKS—Irregular melted glaze caused by contact 
of Pin with body during the melting of the glaze in ghlost 
kilns. They are usually three in number, and is the point 
on which ware rests during this period of fire. 

PIPE CLAY—Fat clays. Ball Clays. 

PISOLITE—A limestone containing concretions of small 
size. 

PLASTER OF PARIS—Partially dehydrated gypsum, or 
calcium sulphate. Is made by the most careful process 
of heat treatment in muffle furnaces or retorts,, and a very 



54 


Ceramic Dictionary 


delicate operation to produce uniform for potting pur¬ 
poses. When this dehydrated plaster is again mixed with 
water, in time it “sets,” caused by the recombination with 
water, to form a hydrated calcium sulphate. The theo¬ 
retical water necessary to accomplish this is 18%, but in 
practice about 30% is used. An excess of water eases 
mixing but retards setting. Plaster has but little expan¬ 
sion, a reason for its broad use. Plaster surfaces may be 
hardened by mixing alum, borax, tartaric acid or alcohol 
in the water, but these substances retard setting. By 
painting the surfaces of mold with melted wax, paraffine, 
or stearin, the pores may be filled and surface made 
smooth, but absorbent action lost. If surface is washed 
with a solution of barium hydroxide it will form barium 
sulphate, and produce a very hard insoluble surface. 
Washing with size or glue makes stucco. Freshly shipped 
plaster should not be used if best results are desired. 
Plaster ages to the extent of a uniform moisture content 
throughout if kept in a dry place, resulting in more uni¬ 
form molds. A five months supply of plaster always 
working on the old end, if kept in a dry place, will pro¬ 
duce more uniform mixing and better molds. 

PLASTIC—Having formative power. Pliable. Impres¬ 
sionable. 

PLASTICITY—Having plastic force. The plasticity of a 
clay depends on the following factors, viz.: the plasticity 
of the alumina in the clay, and its proportion and rela¬ 
tion to other ingredients,—and the nature, size and form 
of grain of other constituent ingredients. 

PLATINUM—A heavy metallic element, the most infus¬ 
ible and resistant of all substances. 

PLUMBERIFEROUS—Lead like, or containing lead or its 
compounds. 



Ceramic Dictionary 


55 


PORCELAIN—From the Italian word, Porcellana, a cow¬ 
rie shell, of a white glazed surface similarity. Porcelain 
is of many varieties—hard, soft, natural, artificial, chem¬ 
ical, electric, high tension, phosphate and dull, and many 
times very difficult to classify, but the word usually indi¬ 
cates vitreous white translucent body, with a transparent 
glaze. All porcelains, to be such, are classed as non¬ 
absorbent, and in most cases the glaze amalgamated with 
the body. Was first made by the Chinese 206 B.C. from 
natural material, and is still made the same way, by about 
the same methods. They use but two materials, “C’hi Ku” 
or bone, is the China Clay itself, and “C’hi ro,” flesh, is a 
flint and feldspar clay. These materials are very impure 
and inferior compared to modern materials, hence the use 
by them of heavy glazes and decoration to hide the im¬ 
perfect body. The first true porcelain was made in 1709 
at Dresden. Electrical and high tension porcelain are not 
true porcelain, but porcelain in name only. 

PORE WATER—Mechanical water. Water retained in 
interstitial spaces, or pores, of a material or body. Water 
which remains in the clay just at the point when shrinkage 
has ceased. It is hence the amount of water obtained by 
subtracting from the total percentage of water in the 
plastic clay the amount of water which corresponds to 
the shrinkage volume. 

POROSITY—Quality or state of being porous. 

POROUS—Containing pores, or air spaces. Porous wares 
are absorbent, the water displacing the air held in the 
pores. 

PORE SPACE—Wall Tile made under pressure is 20% 
porous after firing. In floor tile, or vitreous tile, they dis¬ 
appear, due to the almost complete amalgamation of the 



56 


Ceramic Dictionary 


constituent parts. Earthenware is 27% pore space after 
firing. 

POTASH—An alkali. An ingredient of feldspar and found 
in almost all ceramic materials in some form. 

POT—A container made of clay. To pot,—the production 
of clay articles. 

POTTERS FIELD—Too poor to afford burial the corpse 
was exhumed in the potters kiln and the ashes discarded 
with the refuse in the potters refuse field. 

POTTERS TREE—A Brazilian tree, the wood and bark 
containing high percentage of silica. Silica is derived 
from burned bamboo in Japan. 

POTTERS WHEEL—A round flat wheel on which clay 
is placed for the purpose of throwing and shaping ware 
by hand. A jigger is a mechanical potters wheel. 

POTTERY—A factory for the manufacture of clay articles. 

PO YANG—Lake in China from which locality Chinese 
secure their clays for potting. 

PRESS—See Filter Press or Tile Press. 

PRESSING—The process of making clay articles in a mold 
by hand, using the plastic prepared clay, with the proper 
proportion of water of formation. 

PRIMARY CLAY—Clay located in its first or original 
position as formed by nature from disintegration of rock 
and unmoved by natural waters. 

PRODUCER GAS—An artificial gas made by a producer. 
It contains 53% nitrogen and 25% carbon monoxide and 
has 150 B.T.U. per cubic foot. The most inefficient of 
all pottery fuels. 

PROPS—Cast iron supports for cast iron shelving for plac¬ 
ing decorating kilns. Heavy clay support. 



Ceramic Dictionary 


57 


PULVERIZE—To render fine. 

PUGGING—The process of wedging clay by a vertical or 
horizontal machine, called a Pug Mill, in order to secure 
a uniform ho'mogeneous clay mass. Clay particles from 
this process form themselves in circles. 

PURE WATER—A necessity for the careful manufacture 
of white wares. Iron, titanium, or salt bearing waters all 
have effects in glaze making and body discoloration. 

PYROMETER—An instrument for measuring heat. 

PYROXENE—Usually a calcium magnesium silicate of 
many varieties. Next to feldspar it is the most frequent 
constituent of igneous rocks. 

Q 

QUARTZ—A crystalline form of silica. Usually colorless 
and transparent, but containing impurities which may 
give it various shades and colors, like smoky quartz, or 
other semi-precious stones. Quartz is most common in 
all solid mineral deposits, and an essential constituent of 
granite, and some other rock, and forms itself into solid 
masses of quartzite. When quartz rock is found in suf¬ 
ficient solid mass formations to warrant mining for quartz 
alone, then the variety is used for quartz flint. The great¬ 
est impurity in rock quartz flint is most likely to be a 
form of vegetable iron stain, impossible to weather or 
remove. 

QUARTZITE—Compact granular rock composed of quartz, 
made in nature from metamorphosed sandstone and sili- 
cious cement into a hard homogeneous rock. 

QUARTZOSE—Containing quartz, or resembling quartz. 
Quartz. 

QUARTZ FLINT—Flint made from hard quartz rock. 
The most difficult of all flints to produce. In addition to 
great difficulty in mining it, is most difficult to crush, 




58 


Ceramic Dictionary 


which must be done by first calcining the rock and break¬ 
ing down the structure by dehydration by heat and steam 
cracks. It is usually water ground, a’nd regardless of the 
fineness of grind the grains of flint will retain their clear, 
sharp, crystalline nature. 

QUEENSWARE—Originally a cream colored earthenware. 
The first ware made from English China Clay following 
its discovery in 1725 in Cornwall. The ware was con¬ 
sidered very choice, and in 1760 Wedgewood sold a set 
to Queen Charlotte and thereafter called this variety 
Queensware. Today the word signifies a heavy, white, 
thick ware of inferior quality. 

R 

RAW GLAZE—One having no portions of the glaze fritted 
or calcined. 

REACTION — A chemical transformation or change 
brought about by the coming together of two or more 
compounds. 

REAGENT—Any substance, or chemical, which takes part 
in bringing about reactions for the purpose of examining, 
measuring or detecting other material. 

RECORDS—Something all ceramists should keep. 

RED INK—The commercial test for absorption and poros¬ 
ity. Not so severe as the fuchsine test. 

RED LEAD—Lead tetroxide. Used as a sagger washing 
ingredient, and extensively in glass making. 

REDUCING TEMPERATURE—To restrict or limit or 
retard the use of air in the burning of a fuel, so that there 
is an excess of combustible gases over air, and the gases 
thus seeking oxygen may steal it from the available ox¬ 
ides in the body or glaze. 



Ceramic Dictionary 


59 


REFRACTORY—A material, usually a clay, capable of re¬ 
sisting the action of heat without losing or melting un¬ 
der pressure. A fire clay. A pure china clay. A high grade 
refractory clay must be free, or fairly so, from alkalis, 
iron, or other impurity, as a small quantity of any of these 
reduces qualities materially. 

RESIDUAL CLAY—Clays formed by rock decay and left 
as a residue after the soluble parts have leached out, and 
still in contact with parent bed. 

RING—Sagger bungs are placed in round periodic kilns in 
rings, commonly designated as the first, or outside ring, 
second, third, fourth, etc., dependent upon the size of the 
kiln:—and the center ring, that which surrounds the well 
hole. It is used to designate in which portion of the kiln 
ware is placed, or to be placed. Ware in the first ring, 
or outside ring, and around the well hole, naturally se¬ 
cures greater fire and quicker fire than that further away 
from the flames. 

ROCKINGHAM—Ware with an earthenware body, or 
yellow clay body, covered with a brown or brown spec¬ 
kled glaze usually very lustrous. 

ROCKS—All ceramic material originates in some form ot 
rock. Therefore, in rocks is the beginning of the study 
of ceramics. Flint, sand and quartz, may come from the 
original rock—from metamorphyzed rock, or completely 
disintegrated rock—or partially disintegrated and dis¬ 
solved rock . And may be found near the parent 
rock or carried by water to distant points. There are 
many forms and varieties of feldspars. But all feldspars 
are found in rocks, or among rocks, or as rocks in many 
different states and conditions. Clays are all the result 
of disintegrated and decomposed rocks. Cornwall Stone 
is partially decomposed rock. Paris White and Whiting 



60 


Ceramic Dictionary 


originate in some form of rock, having passed through 
many natural changes. We cannot thoroughly under¬ 
stand the study of ceramics until we possess some gen¬ 
eral knowledge of the subject of rocks. 

ROTTENSTONE—A silicious stone, the residue of a sili- 
cious limestone, the lime of which ha& been removed by 
the solvent action of water. 

RUCKLING—Also called waving, the peeling off of glaze. 
This action is similar to scaling or shivering, except in 
scaling or shivering the glaze is likely to pull off some of 
the body in its peeling action. In ruckling this action 
does not occur, it being merely a scaling action. This is 
due to improper mixes, or improper raw materials, or 
glaze having a too narrow margin of safety in connection 
with the body, or improper flint, or flint content. 

S 

SAGGERS—A refractory fire clay box, or fire clay with 
other material, in which ware is placed for purpose of 
handling, and for protection during the firing period. 

SAGGER CLAY—Any clay used for making saggers. There 
are two distinct varieties for this purpose. One a refrac¬ 
tory clay to resist heat action and the other a bond clay 
to give strength. 

SAGGER MENDER—Many broken, or partially damaged 
saggers can be salvaged for an extra fire or two by the 
use of a sagger mender. There are many mixes with 
about the following constituents—two parts ground fire 
clay, two parts fine grog, two parts sodium silicate, one 
part ball clay, three-quarters part feldspar. 

SAGGER WASH—Flint and clay mixed with water and 
applied by hand to the rim, or bottom of a sagger to 
prevent sticking of wads or points of contact. In ghlost 



61 


Ceramic Dictionary 


saggers this wash is made of a mixture of spar, red lead 
and whiting, and applied by hand to the insides and bot¬ 
toms of saggers to prevent the open porous sagger from 
stealing the volatile glaze from the wares during the 
firing. 

SAL SODA—Sodium carbonate. Used in casting processes 
as a deflocculating agent, and to produce alkaline solution. 

SALTS—Compounds of many materials forming crystals. 

SALTING—That process of glazing certain products, such 
as sewer pipe, etc., by throwing salt on the kiln fires. 
The salt, sodium chloride, decomposes at 1200° C.—cone 
3, acts on the silica on the surface of the ware, forming a 
surface vitrification, or glaze, of sodium silicate. 

SAND—Decomposed rock particles, usually sized and grad¬ 
ed by the washing of natural waters, and deposit of same. 
There are as many kinds of sand as there are rocks, the 
principals of which are—quartz, feldspathic, micaceous, 
ferruginous, calcareous, clay, saline and mixtures of any 
or all. Pure quartz sand is only kind suited for placing 
sand, and this must be free from iron, the same as that 
used for flint. Sand is the principal ingredient of glass 
and must be free from iron although many other impuri¬ 
ties are not considered as such for glass. 

SAND FLINT—Flint made from hard quartz sands of 
great purity. There are many quartz sands, but very 
few sufficiently pure for potters flint. Sand Flint should 
be 99% pure silica, contain practically no lime or iron 
compounds, and of a crystalline nature, sharp and angular. 

SANITARY HEAVY WARE—Ware having an open and 
absorbent fire clay body made with grog and built up 
by hand. Is covered with an englobe, and a heavy im¬ 
permeable thick opaque glaze, and fired in one fire. 




62 


Ceramic Dictionary 


SANITARY WARE—Ware with a rather hard body and 
soft glaze, though not always vitreous and non-absorbent, 
covered with either a translucent or opaque glaze and 
two fires used, bisque and ghlost. 

SANITARY PORCELAIN—Dense heavy hard ware, usu¬ 
ally vitreous and non-absorbent, though not always so. 
Covered with either a translucent or opaque glaze, and 
two fires used, biscuit and ghlost. 

SCALING—Same as shivering. 

SCHIST—Any metamorphic rock having foliated structure 
capable of division in parallel planes, such as mica schists. 

SCUMMING—A common potting ailment and may be 
caused by various things; a too high sulphur coal,—or 
other sulphurous fuel;—sulphur in some materials used, 
or in the water used, even in minute quantities;—grease 
on wares before dipping;—unclean and dirty conditions;— 
fissures which look like scumming caused by detached 
glaze before fire;—improper materials;—or mixes of ma¬ 
terials. 

SEDIMENTARY—Rocks, clay or other material, deposited 
as a sediment from the washing and settling of natural 
waters. 

SEDIMENTATION—The act or process of depositing 
sediment. 

SECOND—Unit of time. 

SECONDARY CLAY—A clay which has been transported 
by natural waters from its place of origin and deposited 
elsewhere. 

SEGER—Herman A.—1870—Famous German ceramist 
and first writer on technical ceramics. 

SELINIUM OXIDE—Used in glass making as a decolor¬ 
izing agent. 




Ceramic Dictionary 


63 


SEMI-VITREOUS—A name for earthenware, or bodies 
of this type. Porous and absorbent. 

SETTLING—A common dipping complaint. Usually 
caused by grinding the glaze with too much water, and 
the remedy is to grind the glaze thicker, using less 
water, regardless of amount added afterwards. Or 
settling may be caused by improper materials, or coarse 
grinding of material, or changing of material. Instant 
relief from this trouble may be remedied by using epsom 
salts in the glaze tub, about 2 Oz. to 1000 Lbs. of batch 
weight. Changing boric acid sometimes causes setth'ng, 
remedied only by epsom salts. 

SETTERS—Heavy, crude, fired ware unglazed, made from 
sagger clay or other crude clay, on which a bung of 
green ware rests for the purpose of handling and firing 
in the bisque kiln, to reduce loss in handling. 

SHAW KILN—A stationary compartment kiln in which 
the waste heat of one chamber preheats other chambers. 

SHIVERING—That condition, the reverse of crazing, in 
which the glaze does not fit the body, so that the ex¬ 
pansion of the body is greater than the glaze, causing 
it to peal off. The remedy for this is just the reverse 
of that for crazing, except that shivering is usually a 
body fault, and not due to underfire, and usually due 
to the use of too highly silicious material, or too high 
flint content in body. 

SHRINKAGE—Variations in shrinkage, sometimes uncon¬ 
trollable, may be due to variations in mechanical water 
in body. Variations of this kind are difficult to control. 
Normal standard shrinkage of pottery bodies is about 
12 %. 

SHORD—Usually broken saggers, or pieces of broken 
saggers. Broken sagger pieces being used for shoring 
bungs in the kiln. May also apply to broken bricks. 



64 


Ceramic Dictionary 


SHORING—Supports used in placing bungs of saggers in 
the kiln. This shoring may be only temporary wooden 
supports or may be permanent pieces of broken saggers, 
or other fire clay material. 

SIEVE—A screen for sizing material, of iron wire, steel 
wire, copper, phosphor-bronze or silk. 

SILEX—Silica in the form of hard water-worn amorphous 
pebbles. 

SILICATE—All potting materials for bodies are silicates, 
or contain silica. Flint is silica; clay is hydrated silicate 
of alumina and feldspar is a potassium-sodium aluminum 
silicate. When these materials amalgamate in a body, 
with other ingredients, or by themselves, they all form 
further complex silicates with each other. A glaze is 
a mechanical mixture of various ingredients before the 
fire, but after the fire the glaze becomes a silicate, or 
a chemical compound of silica. The ceramic industry 
is therefore sometimes called the silicate industry. No 
matter what material is used to start with, a silicate 
of some form is always produced after the fire. 

SILICATE OF SODA—See water glass. 

SILICIOUS—Containing silica, or its compounds, or re¬ 
sembling sand, or sandy. 

SILLIMANITE—A fibrous silicate of alumina consisting 
of one molecule of alumina and one of silica. This 
silicate in the form of needle-like crystals of minute 
size forms in the firing of clays or of porcelains to higher 
temperatures. It is hence the result of the decompo¬ 
sition of clay substance. 

SLIP KILN—Long horizontal brick fire boxes in parti¬ 
tions in which clay slip is run to dry to desired con¬ 
sistency. 




Ceramic Dictionary 


65 


SINTER—To become, or cause to become, a coherent 
solid mass by heating, without thorough melting. 

SMEARING—The evaporation of glaze being deposited 
'on other ware. When this action is desired a mixture 
of common salt, feldspar and white lead is placed in 
sagger to augment this action. 

SMOKING—Coal smoke may cause carbon deposits which 
readily burn off porous wares, but may give a yellow 
tinge to vitreous ware. Smoking, as a rule, is firing 
under reducing conditions. 

SMOKING PERIOD—Or water smoking. That period 
from the time the kiln is first lit up to 700° C. in which 
all water, mechanical and chemical, is liberated from the 
ware. Much ware may be lost during this period if 
heat advances too rapidly, which causes rapid produc¬ 
tion of steam expansion in the ware. 

SOAK—Soaking period. To hold kiln heats without tem¬ 
perature advances to give the heat a chance to soak 
through all portions of the ware in the kiln, in order 
to secure uniformity of texture, vitrification and body. 

SOAK—To permit clays to disintegrate in water. 

SOAPSTONE—Talc. Steatite. 

SODA—Many forms of this element in many ways used 
in ceramics and a natural ingredient of almost all ceramic 
material. 

SODA ASH—Sodium carbonate and sodium hydrate. An 
important glass constituent. 

SODA FELDSPAR—True soda feldspar is albite. But 
reference to soda feldspar in ceramics is usually soda- 
potash feldspar, or anorthoclase feldspar, in which the 
soda content is greater than the potash content. 

SODIUM BICARBONATE—Same as cooking soda. 
Sometimes used in a glaze to augment other material. 



66 


Ceramic Dictionary 


SODIUM CARBONATE—Sal soda. The chief constitu¬ 
ent of soda ash. 

SODIUM CHLORIDE—Common salt. Used as a glazing 
element in certain products. In white ware would act 
to increase vitrification forming a sodium silicate. 

SODIUM HYDRATE—Caustic soda. 

SODIUM SILICATE—Water glass. Used as a suspen¬ 
sion agent in casting bodies and for the mending of 
saggers. 

SODIUM OXIDE—An ingredient of feldspars, contain¬ 
ing soda. 

SOFTENING PERIOD—The third stage of kiln firing, 
when vitrification first appears and the mass becomes 
soft. Any further heat advances would ruin the product 
in biscuit and may cause glazes to boil and bubble. 

SOFT PORCELAIN—See artificial porcelain. 

SOLUBLE—Capable of being dissolved in water. 

SPALLING—To fly to pieces, or chip off, as the edge 
of a stone set with too much weight on the edge. But 
in ceramics is due usually to too rapid firing in the 
water smoking period, in which rapid formation of steam 
causes chips to fall off or the entire piece to fly to pieces. 
Or may be caused by rapid expansion of some body 
ingredient which would cause the same action. 

SPECIFIC GRAVITY—The relative density of a liquid 
or solid to water, and a gas to air. The specific gravity 
of gold is 19, meaning gold is 19 times heavier than 
water. 

SPURS—Small sharp fire clay setters, on which ware rests 
during the firing period to avoid sticking. 

STANNIFEROUS—Containing tin, or its compounds. 
Like tin. 




Ceramic Dictionary 


67 


STARRING—Body and glaze cracks due to a blow, usu¬ 
ally on thin ware. 

STEATITE—Talc. 

STICKY—Having the qualities of adhesion. Viscous, 
viscid, glutinous and tenacious. Excessive plasticity evi¬ 
denced by pronounced adhesion of the clay to the sur¬ 
face of any material touching it. 

STILTS—Fired clay supports of various sizes for the sup¬ 
porting of ware from the bottom to be fired, and avoid 
sticking. 

STILT MARKS—Same as pin marks. See pin marks. 

STONE CHINA—Earthenware of the heavy white granite 
class. Also called ironstone and opaque china. 

STONEWARE—Ware usually heavy, made from natural 
unwashed clays of an alkaline limey nature, and which 
vitrify at cone 10. Glazed on the body with a clear, 
Bristol or Albany Dip glaze and burned in one fire. 

STOPPING—A body cement for filling cracks in biscuit 
ware prior to glazing. It is composed of regular body 

. clay slip, plus a little extra ball clay and flint. 

STRATIFIED—Arranged in layers. 

ST. YRIEUX—Location in France of the natural porcelain 
clays from which French china is made. 

SULPHUR—A very undesirable element in a pottery ma¬ 
terial in any form. It causes scumming, either from 
coal gases, or as a material impurity. 

SUSPENSION—That quality of floating about in a liquid 
without settling to the bottom. 

SYENITE—Any igneous rock dominant in feldspar of any 
kind, and containing various amounts of mica or other 
compounds. 



68 


Ceramic Dictionary 


SYNTHESIS—The reverse of analysis. That process of 
artificially building up of a compound chemically, using 
its elemental parts. Synthetic material may have the 
same chemical analysis as the material reproduced, but 
may be an article entirely foreign to the original, as 
it would be impossible to reproduce the physical quali¬ 
ties by synthesis,—such as hydration and crystalline 
structure. 

T 

TALC—Steatite. A hydrous magnesium silicate. A soft 
rock like material having magnesia as a base. 

TENSILE STRENGTH—The resistance to rupture. Usu¬ 
ally expressed with reference to the unit area of the 
cross section, as the number of pounds necessary to 
produce a rupture. 

TERRA ALBA—Gypsum. 

TERRA COTTA—Artificial building block of any design, 
either glazed or unglazed, having an open porous buff 
colored absorbent body and usually a dense glaze. 

TEXTURE—The manner of the union and fineness of 
particles, or constituent parts of a body or compound. 

TEXAS CLAY—Halloysite. A certain type clay commonly 
known by this name and found in that state. 

THERMIC YIELD—A measure of efficiency. Every 
cubic foot of gas burned, or every ton of coal, or gallon 
of oil consumed should yield so much ware in either 
dozens, pieces or dollars and cents. A basis for establish¬ 
ing costs and enabling the potter to determine if he is 
getting full value for fuel. 

THROWERS WHEEL—Potters wheel operated by powder 
other than the “Thrower”. 

THROWING—The age old process of forming ware by 
hand, and without a mold, usually on a revolving wheel 
turned by the foot or hand power. 




Ceramic Dictionary 


69 


TILE—An artificial floor, wall or roof covering made of 
clays or clays with other material. 

Floor Tile are usually very hard and vitreous and non¬ 
absorbent and unglazed. Wall Tile very open and porous 
and absorbent and glazed. Roofing Tile are hard, vitre¬ 
ous, made of natural clays, or mixtures of clays, both 
glazed and unglazed. There are Faience Tile, Majolica 
Tile, art and many forms and bodies and designs, all 
at various heats. Fire proof building tile are made of 
refractory material. Building Tile usually of dense, 
vitreous clays, salt glazed. Tile made under pressure 
have 20% air space. By Hand 27% air space. 

TILE PRESS—Machine used for manufacture of tile, un¬ 
der pressure, using dampened crushed clays, or clay 
bodies. 

TIN ASH—Tin Oxide. “Ashes of Tin.” 

TITANIUM—Titanic Oxide. A strong coloring usually 
common in some secondary clays. 

TRACHYTE—A volcanic rock of alkaline feldspar of a 
physical nature like porphyry. 

TRANSPARENT GLAZE—Glass-like glaze. In soft 
glazes with lead, or in hard glazes with alumhia and hav¬ 
ing an alkaline base. 

TRICKLING—Heavy glaze running down to lower por¬ 
tions of ware, and particularly that action caused by 
glaze running from dense hard bodied wares. 

TRIDYMITE—A mineral consisting, like quartz, of silica, 
but of a different crystalline form, being usually in 
minute thin tabular forms. 

TRI-SILICATE OF IRON—A fine dust like forrr of iron 
common to certain feldspars found in Canada. 

TURNING—Finishing ware on a lathe by cutting and 
polishing with a tool. 


i 



70 


Ceramic Dictionary 


TUSCANY ACID—A natural boric acid from Italy of 
volcanic origin. Usually more impure than the arti¬ 
ficial acid. Tuscany Acid will run about 79% boric 
crystals, and the balance usually impurities such as sul¬ 
phates of magnesium, soda and ammonia. 


U 

UNDERFIRED—The withdrawal of heat before the prod¬ 
uct has had sufficient time to permit the constituent parts 
of a body to become amalgamated to the desired degree, 
or to become silicates; or a glaze to become sufficiently 
developed, or colors mature. 


UNDERGLAZE—The use of metallic oxide coloring 
agents as a decoration between the body and glaze so 
as to secure permanency for the decoration. The de¬ 
sign is placed or painted on the biscuit ware in the 
same manner it may be placed on the ghlost ware. The 
ware is then fired for the purpose of setting the decora¬ 
tion and burning out the varnish. This is called harden¬ 
ing on, and permits satisfactory glaze dipping. The 
glaze is applied in regular manner and the ware fired 
in ghlost kiln. As a general rule for this purpose: 

Cobalt Oxide is used for blues 


Nickel 
Copper ” 
Manganese Oxide 
Iron Oxide 
Uranium Oxide 
Chromium ” 
Iridium 
Platinum ” 

Gold 


brown 

green or blue green 

brown or violet 

yellow or reds 

yellows 

green or red 

black 

grays 

rich reds 


but all used under certain conditions in order to secure 
desired results. 





Ceramic Dictionary 


71 


V 

VARNISH —Used in decalcomania decoration process by 
painting it on the ware and so cause the decoration on 
the paper to leave it and adhere to the ware. This varnish 
must be very pure and burn out without leaving any 
sediment or scum. 

VAPORIZE —To evaporate. 

VESICULAR —Structure of an open porous nature. 

VINEGAR —Acetic acid. Used is a glaze tub as a first 
aid remedy to retard action of glaze running or trickling 
on hard dense wares. It neutralizes the lime. 

VIRGINIA CLAY —A very fine grade of white residual 
clays found in small pockets in Virginia. America’s finest 
clay, but pockets too small to profit marketing. 

VISCID —Same as Viscous. 

VISCIDITY —Same as Viscosity. 

VISCOSITY —The resistance of the particles of a material 
to flow. Having an adhesive sticky nature. Glutinous 
and ropy like. Having the property of adhering. 

VISCOUS —Having the quality of viscosity, such as gums, 
molasses and tar. A glaze may have this quality under 
heat. Moulten glass is viscous. 

VITREOUS —Glass like. Vitreous clay products have a 
sharp, glassy structure and sharp angular fracture, and 
non-absorbent and impermeable. 

VITRIFIED WARE —Clay wares having both body and 
glaze, non-absorbent and of a vitreous nature. 

VOLT —The unit of electrical force, in which one ohm 
will produce one ampere. 

W 

WACHEINITE —Rocks similar to sandstone in texture, 
though derived from disintegrated and partially decom¬ 
posed basic rocks. 



72 


Ceramic Dictionary 


WADS —A strip of moist day laid on the rim of a sagger, 
to form a bed for the super-imposed sagger and to seal 
the’ contents of a sagger from direct action of gas and 
flame during heating in kiln. 

WAD CLAY —Any clay capable of being used for wads. A 
wad clay should have a sticky nature for molding and ad¬ 
hering to sagger and also an open nature after firing, 
and a minimum contraction. 

WASHING —That process for the refinement and puri¬ 
fication of material, usually clays, by levigation, settling, 
lawning, or other means. 

WATER —There are three kinds of water common to 
ceramic bodies. First, chemical water, or water held 
in chemical combination with the compounds of the body. 
Second, and third, mechanical water, of which there are 
tw r o kinds—hygrometric, or hydroscopic water,—and 
water of formation, or the water required to render the 
mass workable. Chemical water is that retained in the 
body after drying at 120° C., and all of which cannot 
be liberated until 750° C. is reached. All mechanical 
water can be liberated at 120° C. The hygrometric water 
is that absorbed by the material from the air, dependent 
upon the hydroscopic nature of parts. Water of forma¬ 
tion will dry out in any dry air.—Green ware loses its 
water of formation but still has its hygrometric and 
chemical water. Water is 88*4% oxygen and W/ 2 % 
hydrogen. It boils at 212 sea level. Sea water contains 
1}4% salt. For all ceramic purposes water should be 
pure and contain no metallic oxides or salts, as these 
affect color and cleanliness more than generally supposed. 

WATER CORE— In some thick and heavy ceramic bodies 
using molds for shaping, the clay nearest the mold loses 
its water first by absorption into the mold. This clay 




Ceramic Dictionary 


73 


forms a crust, so as not to permit tlie water in the clay 
away from the mold to be absorbed by the mold, or 
to be absorbed only very slowly. A distressing condi¬ 
tion of production. This condition is usually caused by 
too fine grained material, or too much sticky, plastic 
materiaf, or too rapid absorption at first. The remedy 
is the use of proper material, or more opening material, 
or an agent to deflocculate the material. 

WATER GAS —Artificial Gas as generally known, made 
usually by forcing steam over hot coke or coal. It con¬ 
tains 48% hydrogen and 38% carbon monoxide. Con¬ 
tains 300 B. T. U. per cubic foot. Will evaporate 262 lbs. 
of water. See Gaseous Fuels. 

WATER GLASS —Silicate of soda. Having several forms. 
Used as a cement or hardening and binding agent in 
sagger mending;—also as a binding agent in certain other 
products;—and in the casting process as an agent of 
suspension and flocculation;—and also as a hardening and 
deflocculating agent in certain clay slips. 

WATER SMOKING —The first stage of kiln firing, in 
which all mechanical and chemical water is driven from 
the ware. The mechanical water at 120° C. The greatest 
care is required during this period to avoid rapid fire 
and so form steam bubbles in ware. The greatest shrink¬ 
age of ware occurs in this period. 

WATT —The unit of electrical flow. 

WAVELLITE —A phosphate of alumina. 

WAVING —Same as ruckling. 

WAUVER —An inverted empty sagger, super-imposed on 
the rim so as to protect tall ware, which protrudes from 
the top of the lower sagger, which is too shallow to 
house the ware. 




74 


Ceramic Dictionary 


WEATHERING —That process of permitting clays to 
remain in the open to secure the benefits of rain, frost 
and sun, in order to wash the undesirable soluble salts 
from the clay by rain, to break down the structure and 
disintegrate the mass by frost and the sun to dry the 
mass for handling. This process is most successfully 
accomplished if the piled clay is no greater than three 
feet thick and the water drains away from it. Weathered 
Clay is always superior to the same clay unweathered. 

WEDGWOOD —Josiah—1749.—Foremost English potter, 
and usually considered the foremost potter of all ages. 

WEDGING —That process of rendering a clay mass uni¬ 
form, homogeneous and free from air by working and 
kneading it by hand. 

WHITE GRANITE —White earthenware, undecorated, 
usually heavy and thick. 

WHITE METAL— Babbit metal. 

WHITE LEAD —Carbonate of lead. Contains 83.6% lead 
oxide. Should be very pure. If impure will give a 
yellow tint to white glazes. 

WHITING —Calcium carbonate. Prepared from chalk,— 
limestone,—as a by-product, or from other sources of 
lime. Used as a flux and neutralizing agent in potting. 
Should run 97% pure for this purpose, but likely to 
contain quantities of free silica, magnesia or iron com¬ 
pounds which are undesirable. Should be the most finely 
pulverized of all ceramic materials, over 300 mesh. It 
is a very inert, inactive ingredient when burned by itself, 
but in the presence of other ceramic material in a body 
or glaze becomes very active. Precipitated calcium 
carbonate, sold as Whiting, is a by-product. Whiting 




Ceramic Dictionary 


75 


breaks down to 56% lime and 44% of carbon dioxide 
gas. The breaking down starts at 590° C. (Cone 022) 
and continues to 990° C., (Cone 08) when reaction is 
complete and all gas evolved. Almost all whitings have 
a crystalline nature. 

WINDOW —That portion of any ceramic plant which 
should be kept cleanest, as most ceramic products are 
sold on visual appearance and selection cannot be done 
in the dark. 

WITHERITE —Natural barium carbonate. Is 90-95% 
pure. Used in terra cotta, brick, roof tile trades as a 
neutralizing agent to retard whitening action heretofore 
common to finished structures. 1% is the usual content 
in the body. 

Y 

YELLOW WARE —Ware made from yellow burning clays 
and having a clear transparent glaze, usually as household 
articles. 

Z 

ZETTLITZ KAOLIN —A German clay in common use 
in that country. A silicious clay. 

ZINC BLENDE —A ferrous zinc oxide. 

ZINCITE —Native zinc oxide. Called red zinc ore, or red 
zinc oxide. 

ZINC OXIDE —Oxide of zinc. Used in glazes as a flux 
and as a neutralizing agent, to neutralize various tints 
likely to occur in glazes without its use. It # should be 
used on basis of purity. 

ZWERMANN KILN— A twin continuous tunnel kiln of 
open fire type using cars. 



TABLES 

AND 

CHEMICAL FORMULA 


78 


Ceramic Dictionary 


MATURING MELTING TEMPERATURES 
STANDARD SEGER PYROMETRIC CONES 



Degrees 


Degrees 

Cone 

Centigrade 

Fahrenheit 

022. 

. 590 


1094 

021. 

. 620 


1148 

020. 

. 650 


1202 

019. 

. 680 


1256 

018. 

. 710 

Liquid 

1310 

017. 

. 740 

Bright Gold 1364 

016. 

. 770 


1418 

015. 

. 800 


1472 

ouy 2 . 

. 875 

Bronze 

1607 

010. 

. 950 

Silver 

1742 

09. 

. 970 


1778 

08. 

. 990 


1814 

07. 

. 1010 


1850 

06. 

. 1030 


1888 

05. 

. 1050 

Copper 

1922 

04. 


.Gold 

1958 

03. 

. 1090 


1994 

02. 



2030 

01. 



2066 

1 . 

. 1150 


2102 

2. 

. 1170 


2138 

3...:. 

. 1190 


2174 

4. 

. 1210 


2210 

5. 

. 1230 

Cast Iron 

2246 

6 . 

. 1250 


2282 




























Ceramic Dictionary 


79 


MATURING MELTING TEMPERATURES 
STANDARD SEGER PYROMETRIC CONES 



Degrees 


Degrees 

Cone 

Centigrade 

Fahrenheit 

7. 

. 1270 


2318 

8. 

. 1290 

Albany Dip 

2354 

9. 

. 1310 

Flint Glass 

2390 

10. 

. 1330 


2426 

11. 

. 1350 


2462 

12. 

. 1370 


2498 

13. 

. 1390 

Steel 

2534 

14. 

. 1410 


2570 

15. 

. 1430 


2606 

16. 

. 1450 


2642 

17. 

. 1470 


2678 

18. 

. 1490 


2714 

19. 

. 1510 

Wrought 

2750 

20. 

. 1530 

Iron 

2786 

26. 

. 1650 


3002 

27. 

. 1670 


3038 

28. 

. 1690 


3074 

29. 

. 1710 


3110 

30. 

. 1730 


3146 

31. 

. 1750 


3182 

32. 

. 1770 


3218 

33. 

. 1790 


3254 

34. 

. 1810 


3290 

35. 

. 1830 


3326 

36. 

. 1850 

Platinum 

3362 


Numbers 21-25 fail to show proper temperature differ¬ 
ences, and are not used under commercial conditions. 




























80 


Ceramic Dictionary 


RELATION OF BRASS, SILK, AND XX SILK LAWN 

Size of Opening 

in Inches Brass 

.0055. 100 

.0046. 120 

.0043. 130 

.0042. 140 

.0038. 160 

Silk 

.0058. 10 

.0052. 11 

.0049. 12 

.0045. 13 

.0039.14 

.0036.** 15 

.0035. 16 

XX Silk 

.0054. 10 

.0047. 11 

.0041. 12 

.0039.13 

.0033. 14 

Therefore, per example: A 130 Brass is nearest equiva¬ 
lent to a No. 13 Silk, and No. 12 XX Silk. 




















Ceramic Dictionary 


81 


A LAWN ANALYSIS OF A SAND FLINT FOR 
POTTERS USE 


160 Mesh Brass 


140 Mesh Brass 


Residue 


Residue 



6 %. 

..240... 

.9.00% 

Difference 

3% 

3.9%. 

..200... 

.9.00% 

Difference 

5.1% 

2.5%. 

00 

o 

.8.00% 

Difference 

5.5% 

1.25%. 

..160... 

.4.00% 

Difference 

2.75% 

1.25%. 

..130... 

.3.00% 

Difference 

1.75% 

0 .00%. 

..110... 

.1.25% 

Difference 

1.25% 


A Lawn analysis of a Potash Feldspar for China manu¬ 
facture of fine grinding: 

A total of 2.7% Residue on 240 mesh 

A total of 2.17% Residue on 200 mesh 

A total of 0.5% Residue on 160 mesh 















82 


Ceramic Dictionary 


CLAY 

Pure Clay exists only in theory, with the possible excep¬ 
tion of the Pure Crystalline Kaolinite, which is exceedingly 
rare. In nature Pure Clays do not exist on a commercial 
scale. Their imaginary formula would be: 

39.77 Alumina 
46.33 Silica 
13.90 Water 


100.00 

A Chemical comparison of seven well known brands of 
English China Clay, Zettlitz Kaolin, and an American China 


Clay. 

1 

2 

3 

4 

5 

6 

7 

Zettlitz 

Amer. 

ican 


Eng. 

Eng. 

Eng. 

Eng. 

Eng. 

Eng. 

Eng. 

Kaolin 

Clay 

Silica.. .. 

42.73 

42.31 

41.30 

44.46 

42.20 

45.51 

47.83 

47.57 

44.40 

Alumina. 

35.20 

34.37 

34.42 

37.00 

34.67 

38.90 

37.66 

38.18 

40.41 

Oxide of 
Iron... 

0.35 

0.43 

0.48 

0.62 

0.33 

0.84 

0.21 

0.84 

0.72 

Lime. ... 

0.18 

0.18 

0.29 

0.27 

0.32 

0.27 

0.51 

0.29 

0.28 

Potash & 
Soda.. 

0.52 

0.74 

0.66 

0.70 

0.41 

0.88 

1.18 

0.70 

0.63 

Magnesia, 
Manganese 
& Titan¬ 
ium . 

None 

None 

None 

None 

None 

None 

None 

.07 

traces 

Combined 
Water & 
Loss. 

11.58 

10.85 

11.54 

11.94 

11.28 

12.11 

12.61 

12.93 

13.90 

Moisture 

9.44 

11.12 

11.31 

5.01 

10.79 

1.48 

..... 

. 






Ceramic Dictionary 


83 


FELDSPAR 

Pure Feldspar, of the common, or orthoclase, variety, 
exists only in theory. In nature they do not exist. 

Its imaginary formula would be: 


Silica . 64.70 

Alumina . 18.40 

Potash . 16.90 


100.00 

A Chemical Comparison of seven well known brands of 
Commercial Feldspar in use: 


1 2 3 4 5 6 7 

Silica .69.50 69.40 71.09 65.95 65.33 66.60 66.45 

Alumina ....16.97 16.94 16.80 18.00 20.96 19.20 19.45 

Iron-.07 .11 .14 .12 .71 .10 .07 

Lime.29 .30 .31 1.05 .00 .23 Tr. 

Magnesia ... .13 .03 .00 Tr. .00 .00 .11 

Potash . 9.50 12.20 7.16 12.13 10.63 10.90 11.04 

Soda . 3.24 1.78 4.50 2.11 1.37 3.10 2.75 

Ignition .30 .23 .16 .10 


Sand Rock Flints are found fairly pure in nature, but re¬ 
quire some washing. They will analyze about as follows: 


Silica . 

. 98.749% 

Alumina . 

. 0.195% 

Iron . 

. 0.039% 

Lime . 

. 0.024% 

Magnesia . 

. 0.003% 

Ignition . 

. 0.160% 



















84 


Ceramic Dictionary 


Ball Clays will analyze about as follows: 


1 

Silica . 50.55 

Titanic Oxide . 0.95 

Alumina . 32.80 

Ferric Oxide . 1.30 

Magnesia . 0.41 

Lime . 0.56 

Potash . 3.56 

Soda . 0.87 

Loss when calcined over 100° C. 9.20 


Number 1 is a very high grade tough plastic, 


2 

49.18 

2.77 

31.70 

.98 

.58 

.98 


2.82 

10.87 

vitreous 


burning clay. Number 2 is not a good plastic clay, not a 


good binder and fires open and refractory. 


Average volumetric analyses, and the weight and calorific 
value of 1,000 cubic feet of the four types of gas used for 
heating and illuminating purposes: 



Natural Coal 

Water 

Producer Gas 


Gas 

Gas 

Gas 

Anthra. 

Bitum. 

Carbon Monoxide, CO. . . . 

0.50 

6.0 

45.0 

27.0 

27.0 

Hydrogen, H. 

2.18 

46.0 

45.0 

12.0 

12.0 

Methane, CH. 

92.6 

40.0 

2.0 

1.2 

2.5 

Ethylene, C 2 H. 

0.31 

4.0 

... * 

• • • • 

0.4 

Carbon Dioxide, CO,. 

0.26 

0.5 

4.0 

2.5 

2'. 5 

Nitrogen, N . 

3.61 

1.5 

2.0 

57.0 

55.3 

Oxygen, O . 

0.34 

0.5 

0.5 

0.3 

0.3 

Pounds in 1,000 cu. ft.... 

45.6 

32.0 

45.6 

65.6 

65.9 

B.t.u. in 1,000 cu. ft. 

1 , 100,000 

735,000 

322,000 

137,455 

156,917 

The following table shows 

to what extent 

differences in 

chemical composition 

occur in 

various gases: 






Carbon 


B.t.u. 

Methane 

Ethane 

Dioxide 

Nitrogen 

per 

Source of Gas 

ch 4 

C,H fi 

c ° 2 

N 

cu. ft. 

Texarkana, Ark. 

96.0 

0.0 

0 . 8 " 

3.2 

1.022 

Noblesville, Ind. 

86.8 

6.2 

0.8 

6.2 

1.040 

Leavenworth, Kan. 

91.3 

4.5 

0.8 

3.4 

1.066 

Erie, N. Y. 

79.9 

15.2 

0.0 

4.9 

1.134 

Columbus, Ohio . 

80.4 

18.1 

0.0 

1.5 

1.193 

Guthrie, Okla. 

69.4 

20.6 

0.1 

9.9 

1.062 

Pawhuska, Okla. 

66.5 

20.7 

0.3 

12.5 

1.093 

Fort Worth, Texas. 

51.3 

10.4 

0.1 

38.2 

740 

Bow Island, Canada. 

87.6 

0.9 

• . . 

11.2 
































U. S. GALLONS IN ROUND TANKS 

For One Foot in Depth. 


Dia. 

of 

Tanks. 

No. 

U. S. 
Gals. 

Cubic Ft. 

and Area. 

j in Sq. Ft 

Dia. 

cf 

Tanks. 

No. 

U.S. 

Gals. 

Cubic Ft. 

and Area 

in Sq. Ft. 

Dia. 

of 

Tanks. 

No. 

U. S. 
Gals. 

Cubic Ft. 

and Area 

in Sq. Ft. 

1 

ft. 

5.87 

.785 

5 ft. 8in. 

186.66 

25.22 

19 ft. 

2120.90 

283.53 

1 

1 in. 

6.89 

.922 

5 

9 

198.25 

25.97 

19 

3 in. 

2177.10 

291.04 

1 

2 

8. 

1.069 

5 

10 

199.92 

26.73 

19 

6 

2234. 

298.65 

1 

3 

9.18 

1.227 

5 

11 

201.67 

27.49 

19 

9 

2291.70 

306.35 

1 

4 

10.44 

1.396 

6 


212.51 

28.27 

20 


2350.10 

314.16 

1 

5 

11.79 

1.576 

6 

3 

220.50 

30.68 

20 

3 

2409.20 

322.06 

1 

6 

13.22 

1.767 

6 

6 

245.23 

33.18 

20 

6 

2469.10 

330.06 

1 

7 

14.73 

1.969 

6 

9 

267.69 

35.78 

20 

9 

2529.60 

338.16 

1 

8 

16.32 

2.182 

7 


287.88 

38.48 

21 


2591. 

346.36 

1 

9 

17.99 

2.405 

7 

3 

308.81 

41.28 

21 

3 

2653. 

354.66 

1 

10 

19.75 

2.640 

7 

6 

330.48 

44.18 

21 

6 

2715.80 

363.05 

1 

11 

21.58 

2.885 

7 

9 

352.88 

47.17 

21 

9 

2779.30 

371.54 

2 


23.50 

3.142 

8 


376.01 

50.27 

22 


2843.60 

380.13 

2 

1 

25.50 

3.409 

8 

3 

399.88 

53.46 

22 

3 

2908.60 

388.82 

2 

2 

27.58 

3.687 

8 

6 

424.48 

56.75 

22 

6 

2974.30 

397.61 

2 

3 

29.74 

3.976 

8 

9 

449.82 

60.13 

22 

9 

3040.80 

406.49 

2 

4 

31.99 

4.276 

9 


475.89 

63.62 

23 


3108. 

415.48 

2 

5 

34.31 

4.587 

9 

3 

502.70 

67.20 

23 

3 

3175.90 

424.56 

2 

6 

36.72 

4.906 

9 

6 

530.24 

70.88 

23 

6 

3244.60 

433.74 

2 

7 

39.21 

5.241 

9 

9 

558.51 

74.66 

23 

9 

3314. 

443.01 

2 

8 

41.78 

5.585 

10 


587.52 

78.54 

24 


3384.10 

452.39 

2 

9 

44.43 

5.940 

10 

3 

617.26 

82.52 

24 

3 

3455. 

461.86 

2 

10 

47.16 

6.305 

10 

6 

640.74 

86.59 

24 

6 

3526.60 

471.44 

2 

11 

49.98 

6.681 

10 

9 

. 678.95 

90.76 

24 

9 

3598.90 

481.11 

3 


52.28 

7.069 

11 


710.90 

95.03 

25 


3672. 

490.87 

3 

1 

55.8f 

7.467 

11 

3 

748.58 

99.40 

25 

3 

3745.80 

500.74 

3 

2 

58.92 

7.876 

11 

6 

776.99 

103.87 

25 

6 

3820.30 

510.71 

0 

3 

62.06 

8.296 

11 

9 

811.14 

108.43 

25 

9 

3895.60 

520.77 

3 

4 

65.28 

8.727 

12 


846.03 

113.10 

26 


3971.60 

530.93 

3 

5 

68.58 

9.168 

12 

3 

881.65 

117.86 

26 

3 

4048.40 

541.19 

3 

6 

71.97 

9.621 

12 

6 

918. 

122.72 

26 

6 

4125.90 

551.55 

3 

7 

75.44 

10.085 

12 

9 

955.09 

127.68 

26 

9 

4204.10 

562. 

3 

8 

78.99 

10.559 

13 


992.91 

132.73 

27 


4283. 

572.66 

3 

9 

82.62 

11.045 

13 

3 

1031.50 

137.89 

27 

3 

4362.70 

583.21 

3 

10 

86.33 

11.451 

13 

6 

1079.80 

143.14 

27 

6 

4443.10 

593.96 

3 

11 

90.13 

12.048 

13 

9 

1110.80 

148.49 

27 

9 

4524.30 

604.81 

4 


94. 

12.566 

14 


1151.50 

153.94 

28 


4606.20 

615.75 

4 

1 

97.96 

13.095 

14 

3 

1193. 

159.48 

28 

3 

4688.80 

626.80 

4 

2 

102. 

13.635 

14 

6 

1285.30 

165.13 

28 

6 

4772.10 

647.94 

4 

3 

106.12 

14.186 

14 

9 

1278.20 

170.87 

28 

9 

4856.20 

649.18 

4 

4 

110.32 

14.748 

15 


1321.90 

176.71 

29 


4941. 

660.52 

4 

5 

114.61 

15.321 

15 

3 

1366.40 

182.65 

29 

3 

5026.60 

671.96 

4 

6 

118.97 

15.90 

15 

6 

1411.50 

188.69 

29 

6 

5112.90 

683.40 

4 

7 

123.42 

16.50 

15 

9 

1487.40 

194.83 

29 

9 

5199.90 

695.13 

4 

8 

127.95 

17.10 

16 


1504.10 

201.06 

30 


5287.70 

706.86 

4 

9 

132.56 

17.72 

16 

3 

1591.40 

207.39 

30 

3 

5376.20 

718.69 

4 

10 

137.25 

18.35 

16 

6 

1599.50 

213.82 

30 

6 

5465.40 

730.62 

4 

11 

142.02 

18.99 

16. 

9 

1608.40 

220.35 

30 

9 

5555.40 

742.64 

5 


146.88 

19.63 

17 


1697.90 

226.98 

31 


5646.10 

754.77 

5 

1 

151.82 

20.29 

17 

3 

1748.20 

233.71 

31 

3 

5737.50 

766.99 

5 

2 

156.83 

20.97 

17 

6 

1799.30 

240.53 

31 

6 

5829.70 

779.31 

5 

3 

161.93 

21.65 

17 

9 

1861.10 

247.45 

31 

9 

5922.60 

791.73 

5 

4 

167.12 

22.34 

18 


1903.60 

254.47 

32 


6016.20 

804.25 

5 

5 

172.38 

23.04 

18 

3 

1956.80 

261.59 

32 

3 

6110.60 

816.86 

5 

6 

177.72 

23.76 

18 

6 

2010.80 

268.80 

32 

6 

6205.70 

829.58 

5 

7 

183.15 

24.48 

18 

9 

2065.50 

276.12 

32 

9 

6301.50 

842.39 


31H Gallons equals 1 Barrel. 

To find the capacity of tanks greater than the largest given in the table, look in the table 
for a Tank of one-halt of the given size and multiply its capacity by 4, or one ot one-third 
its size and multiply its capacity by 9, etc. 











































MEMORANDA 



f 










































« 




V 












» 

































































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Ceramic Dictionary 

An invaluable hand book for The Potter, 
Tile and Terra Cotta Manufacturer, those 
engaged in the Silicate Industry, and 
Students of Ceramics. 




JUL o • 1924 












